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e73d4376 |
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14-May-2022 |
Al Viro <viro@zeniv.linux.org.uk> |
convert sgx_set_attribute() to fdget()/fdput() Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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89e927bb |
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15-Nov-2022 |
Kristen Carlson Accardi <kristen@linux.intel.com> |
x86/sgx: Replace kmap/kunmap_atomic() calls kmap_local_page() is the preferred way to create temporary mappings when it is feasible, because the mappings are thread-local and CPU-local. kmap_local_page() uses per-task maps rather than per-CPU maps. This in effect removes the need to disable preemption on the local CPU while the mapping is active, and thus vastly reduces overall system latency. It is also valid to take pagefaults within the mapped region. The use of kmap_atomic() in the SGX code was not an explicit design choice to disable page faults or preemption, and there is no compelling design reason to using kmap_atomic() vs. kmap_local_page(). Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Link: https://lore.kernel.org/linux-sgx/Y0biN3%2FJsZMa0yUr@kernel.org/ Link: https://lore.kernel.org/r/20221115161627.4169428-1-kristen@linux.intel.com
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133e049a |
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05-Sep-2022 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Do not fail on incomplete sanitization on premature stop of ksgxd Unsanitized pages trigger WARN_ON() unconditionally, which can panic the whole computer, if /proc/sys/kernel/panic_on_warn is set. In sgx_init(), if misc_register() fails or misc_register() succeeds but neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be prematurely stopped. This may leave unsanitized pages, which will result a false warning. Refine __sgx_sanitize_pages() to return: 1. Zero when the sanitization process is complete or ksgxd has been requested to stop. 2. The number of unsanitized pages otherwise. Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list") Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u Link: https://lkml.kernel.org/r/20220906000221.34286-2-jarkko@kernel.org
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a0506b3b |
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10-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Free up EPC pages directly to support large page ranges The page reclaimer ensures availability of EPC pages across all enclaves. In support of this it runs independently from the individual enclaves in order to take locks from the different enclaves as it writes pages to swap. When needing to load a page from swap an EPC page needs to be available for its contents to be loaded into. Loading an existing enclave page from swap does not reclaim EPC pages directly if none are available, instead the reclaimer is woken when the available EPC pages are found to be below a watermark. When iterating over a large number of pages in an oversubscribed environment there is a race between the reclaimer woken up and EPC pages reclaimed fast enough for the page operations to proceed. Ensure there are EPC pages available before attempting to load a page that may potentially be pulled from swap into an available EPC page. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/a0d8f037c4a075d56bf79f432438412985f7ff7a.1652137848.git.reinette.chatre@intel.com
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c7c6a8a6 |
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10-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Make sgx_ipi_cb() available internally The ETRACK function followed by an IPI to all CPUs within an enclave is a common pattern with more frequent use in support of SGX2. Make the (empty) IPI callback function available internally in preparation for usage by SGX2. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/1179ed4a9c3c1c2abf49d51bfcf2c30b493181cc.1652137848.git.reinette.chatre@intel.com
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f89c2f9b |
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10-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Move PTE zap code to new sgx_zap_enclave_ptes() The SGX reclaimer removes page table entries pointing to pages that are moved to swap. SGX2 enables changes to pages belonging to an initialized enclave, thus enclave pages may have their permission or type changed while the page is being accessed by an enclave. Supporting SGX2 requires page table entries to be removed so that any cached mappings to changed pages are removed. For example, with the ability to change enclave page types a regular enclave page may be changed to a Thread Control Structure (TCS) page that may not be accessed by an enclave. Factor out the code removing page table entries to a separate function sgx_zap_enclave_ptes(), fixing accuracy of comments in the process, and make it available to the upcoming SGX2 code. Place sgx_zap_enclave_ptes() with the rest of the enclave code in encl.c interacting with the page table since this code is no longer unique to the reclaimer. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/b010cdf01d7ce55dd0f00e883b7ccbd9db57160a.1652137848.git.reinette.chatre@intel.com
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bdaa8799 |
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10-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Rename sgx_encl_ewb_cpumask() as sgx_encl_cpumask() sgx_encl_ewb_cpumask() is no longer unique to the reclaimer where it is used during the EWB ENCLS leaf function when EPC pages are written out to main memory and sgx_encl_ewb_cpumask() is used to learn which CPUs might have executed the enclave to ensure that TLBs are cleared. Upcoming SGX2 enabling will use sgx_encl_ewb_cpumask() during the EMODPR and EMODT ENCLS leaf functions that make changes to enclave pages. The function is needed for the same reason it is used now: to learn which CPUs might have executed the enclave to ensure that TLBs no longer point to the changed pages. Rename sgx_encl_ewb_cpumask() to sgx_encl_cpumask() to reflect the broader usage. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/d4d08c449450a13d8dd3bb6c2b1af03895586d4f.1652137848.git.reinette.chatre@intel.com
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7f391752 |
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10-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Export sgx_encl_ewb_cpumask() Using sgx_encl_ewb_cpumask() to learn which CPUs might have executed an enclave is useful to ensure that TLBs are cleared when changes are made to enclave pages. sgx_encl_ewb_cpumask() is used within the reclaimer when an enclave page is evicted. The upcoming SGX2 support enables changes to be made to enclave pages and will require TLBs to not refer to the changed pages and thus will be needing sgx_encl_ewb_cpumask(). Relocate sgx_encl_ewb_cpumask() to be with the rest of the enclave code in encl.c now that it is no longer unique to the reclaimer. Take care to ensure that any future usage maintains the current context requirement that ETRACK has been called first. Expand the existing comments to highlight this while moving them to a more prominent location before the function. No functional change. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/05b60747fd45130cf9fc6edb1c373a69a18a22c5.1652137848.git.reinette.chatre@intel.com
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0c9782e2 |
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20-May-2022 |
Kristen Carlson Accardi <kristen@linux.intel.com> |
x86/sgx: Set active memcg prior to shmem allocation When the system runs out of enclave memory, SGX can reclaim EPC pages by swapping to normal RAM. These backing pages are allocated via a per-enclave shared memory area. Since SGX allows unlimited over commit on EPC memory, the reclaimer thread can allocate a large number of backing RAM pages in response to EPC memory pressure. When the shared memory backing RAM allocation occurs during the reclaimer thread context, the shared memory is charged to the root memory control group, and the shmem usage of the enclave is not properly accounted for, making cgroups ineffective at limiting the amount of RAM an enclave can consume. For example, when using a cgroup to launch a set of test enclaves, the kernel does not properly account for 50% - 75% of shmem page allocations on average. In the worst case, when nearly all allocations occur during the reclaimer thread, the kernel accounts less than a percent of the amount of shmem used by the enclave's cgroup to the correct cgroup. SGX stores a list of mm_structs that are associated with an enclave. Pick one of them during reclaim and charge that mm's memcg with the shmem allocation. The one that gets picked is arbitrary, but this list almost always only has one mm. The cases where there is more than one mm with different memcg's are not worth considering. Create a new function - sgx_encl_alloc_backing(). This function is used whenever a new backing storage page needs to be allocated. Previously the same function was used for page allocation as well as retrieving a previously allocated page. Prior to backing page allocation, if there is a mm_struct associated with the enclave that is requesting the allocation, it is set as the active memory control group. [ dhansen: - fix merge conflict with ELDU fixes - check against actual ksgxd_tsk, not ->mm ] Cc: stable@vger.kernel.org Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Link: https://lkml.kernel.org/r/20220520174248.4918-1-kristen@linux.intel.com
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0e4e729a |
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12-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Obtain backing storage page with enclave mutex held Haitao reported encountering a WARN triggered by the ENCLS[ELDU] instruction faulting with a #GP. The WARN is encountered when the reclaimer evicts a range of pages from the enclave when the same pages are faulted back right away. The SGX backing storage is accessed on two paths: when there are insufficient free pages in the EPC the reclaimer works to move enclave pages to the backing storage and as enclaves access pages that have been moved to the backing storage they are retrieved from there as part of page fault handling. An oversubscribed SGX system will often run the reclaimer and page fault handler concurrently and needs to ensure that the backing store is accessed safely between the reclaimer and the page fault handler. This is not the case because the reclaimer accesses the backing store without the enclave mutex while the page fault handler accesses the backing store with the enclave mutex. Consider the scenario where a page is faulted while a page sharing a PCMD page with the faulted page is being reclaimed. The consequence is a race between the reclaimer and page fault handler, the reclaimer attempting to access a PCMD at the same time it is truncated by the page fault handler. This could result in lost PCMD data. Data may still be lost if the reclaimer wins the race, this is addressed in the following patch. The reclaimer accesses pages from the backing storage without holding the enclave mutex and runs the risk of concurrently accessing the backing storage with the page fault handler that does access the backing storage with the enclave mutex held. In the scenario below a PCMD page is truncated from the backing store after all its pages have been loaded in to the enclave at the same time the PCMD page is loaded from the backing store when one of its pages are reclaimed: sgx_reclaim_pages() { sgx_vma_fault() { ... mutex_lock(&encl->lock); ... __sgx_encl_eldu() { ... if (pcmd_page_empty) { /* * EPC page being reclaimed /* * shares a PCMD page with an * PCMD page truncated * enclave page that is being * while requested from * faulted in. * reclaimer. */ */ sgx_encl_get_backing() <----------> sgx_encl_truncate_backing_page() } mutex_unlock(&encl->lock); } } In this scenario there is a race between the reclaimer and the page fault handler when the reclaimer attempts to get access to the same PCMD page that is being truncated. This could result in the reclaimer writing to the PCMD page that is then truncated, causing the PCMD data to be lost, or in a new PCMD page being allocated. The lost PCMD data may still occur after protecting the backing store access with the mutex - this is fixed in the next patch. By ensuring the backing store is accessed with the mutex held the enclave page state can be made accurate with the SGX_ENCL_PAGE_BEING_RECLAIMED flag accurately reflecting that a page is in the process of being reclaimed. Consistently protect the reclaimer's backing store access with the enclave's mutex to ensure that it can safely run concurrently with the page fault handler. Cc: stable@vger.kernel.org Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") Reported-by: Haitao Huang <haitao.huang@intel.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Haitao Huang <haitao.huang@intel.com> Link: https://lkml.kernel.org/r/fa2e04c561a8555bfe1f4e7adc37d60efc77387b.1652389823.git.reinette.chatre@intel.com
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#
6bd42964 |
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12-May-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Disconnect backing page references from dirty status SGX uses shmem backing storage to store encrypted enclave pages and their crypto metadata when enclave pages are moved out of enclave memory. Two shmem backing storage pages are associated with each enclave page - one backing page to contain the encrypted enclave page data and one backing page (shared by a few enclave pages) to contain the crypto metadata used by the processor to verify the enclave page when it is loaded back into the enclave. sgx_encl_put_backing() is used to release references to the backing storage and, optionally, mark both backing store pages as dirty. Managing references and dirty status together in this way results in both backing store pages marked as dirty, even if only one of the backing store pages are changed. Additionally, waiting until the page reference is dropped to set the page dirty risks a race with the page fault handler that may load outdated data into the enclave when a page is faulted right after it is reclaimed. Consider what happens if the reclaimer writes a page to the backing store and the page is immediately faulted back, before the reclaimer is able to set the dirty bit of the page: sgx_reclaim_pages() { sgx_vma_fault() { ... sgx_encl_get_backing(); ... ... sgx_reclaimer_write() { mutex_lock(&encl->lock); /* Write data to backing store */ mutex_unlock(&encl->lock); } mutex_lock(&encl->lock); __sgx_encl_eldu() { ... /* * Enclave backing store * page not released * nor marked dirty - * contents may not be * up to date. */ sgx_encl_get_backing(); ... /* * Enclave data restored * from backing store * and PCMD pages that * are not up to date. * ENCLS[ELDU] faults * because of MAC or PCMD * checking failure. */ sgx_encl_put_backing(); } ... /* set page dirty */ sgx_encl_put_backing(); ... mutex_unlock(&encl->lock); } } Remove the option to sgx_encl_put_backing() to set the backing pages as dirty and set the needed pages as dirty right after receiving important data while enclave mutex is held. This ensures that the page fault handler can get up to date data from a page and prepares the code for a following change where only one of the backing pages need to be marked as dirty. Cc: stable@vger.kernel.org Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") Suggested-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Haitao Huang <haitao.huang@intel.com> Link: https://lore.kernel.org/linux-sgx/8922e48f-6646-c7cc-6393-7c78dcf23d23@intel.com/ Link: https://lkml.kernel.org/r/fa9f98986923f43e72ef4c6702a50b2a0b3c42e3.1652389823.git.reinette.chatre@intel.com
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#
e5733d8c |
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02-Feb-2022 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Fix missing poison handling in reclaimer The SGX reclaimer code lacks page poison handling in its main free path. This can lead to avoidable machine checks if a poisoned page is freed and reallocated instead of being isolated. A troublesome scenario is: 1. Machine check (#MC) occurs (asynchronous, !MF_ACTION_REQUIRED) 2. arch_memory_failure() is eventually called 3. (SGX) page->poison set to 1 4. Page is reclaimed 5. Page added to normal free lists by sgx_reclaim_pages() ^ This is the bug (poison pages should be isolated on the sgx_poison_page_list instead) 6. Page is reallocated by some innocent enclave, a second (synchronous) in-kernel #MC is induced, probably during EADD instruction. ^ This is the fallout from the bug (6) is unfortunate and can be avoided by replacing the open coded enclave page freeing code in the reclaimer with sgx_free_epc_page() to obtain support for poison page handling that includes placing the poisoned page on the correct list. Fixes: d6d261bded8a ("x86/sgx: Add new sgx_epc_page flag bit to mark free pages") Fixes: 992801ae9243 ("x86/sgx: Initial poison handling for dirty and free pages") Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/dcc95eb2aaefb042527ac50d0a50738c7c160dac.1643830353.git.reinette.chatre@intel.com
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2056e298 |
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04-Jan-2022 |
Dave Hansen <dave.hansen@linux.intel.com> |
x86/sgx: Fix NULL pointer dereference on non-SGX systems == Problem == Nathan Chancellor reported an oops when aceessing the 'sgx_total_bytes' sysfs file: https://lore.kernel.org/all/YbzhBrimHGGpddDM@archlinux-ax161/ The sysfs output code accesses the sgx_numa_nodes[] array unconditionally. However, this array is allocated during SGX initialization, which only occurs on systems where SGX is supported. If the sysfs file is accessed on systems without SGX support, sgx_numa_nodes[] is NULL and an oops occurs. == Solution == To fix this, hide the entire nodeX/x86/ attribute group on systems without SGX support using the ->is_visible attribute group callback. Unfortunately, SGX is initialized via a device_initcall() which occurs _after_ the ->is_visible() callback. Instead of moving SGX initialization earlier, call sysfs_update_group() during SGX initialization to update the group visiblility. This update requires moving the SGX sysfs code earlier in sgx/main.c. There are no code changes other than the addition of arch_update_sysfs_visibility() and a minor whitespace fixup to arch_node_attr_is_visible() which checkpatch caught. CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-sgx@vger.kernel.org Cc: x86@kernel.org Fixes: 50468e431335 ("x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node") Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/20220104171527.5E8416A8@davehans-spike.ostc.intel.com
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50468e43 |
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16-Nov-2021 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node == Problem == The amount of SGX memory on a system is determined by the BIOS and it varies wildly between systems. It can be as small as dozens of MB's and as large as many GB's on servers. Just like how applications need to know how much regular RAM is available, enclave builders need to know how much SGX memory an enclave can consume. == Solution == Introduce a new sysfs file: /sys/devices/system/node/nodeX/x86/sgx_total_bytes to enumerate the amount of SGX memory available in each NUMA node. This serves the same function for SGX as /proc/meminfo or /sys/devices/system/node/nodeX/meminfo does for normal RAM. 'sgx_total_bytes' is needed today to help drive the SGX selftests. SGX-specific swap code is exercised by creating overcommitted enclaves which are larger than the physical SGX memory on the system. They currently use a CPUID-based approach which can diverge from the actual amount of SGX memory available. 'sgx_total_bytes' ensures that the selftests can work efficiently and do not attempt stupid things like creating a 100,000 MB enclave on a system with 128 MB of SGX memory. == Implementation Details == Introduce CONFIG_HAVE_ARCH_NODE_DEV_GROUP opt-in flag to expose an arch specific attribute group, and add an attribute for the amount of SGX memory in bytes to each NUMA node: == ABI Design Discussion == As opposed to the per-node ABI, a single, global ABI was considered. However, this would prevent enclaves from being able to size themselves so that they fit on a single NUMA node. Essentially, a single value would rule out NUMA optimizations for enclaves. Create a new "x86/" directory inside each "nodeX/" sysfs directory. 'sgx_total_bytes' is expected to be the first of at least a few sgx-specific files to be placed in the new directory. Just scanning /proc/meminfo, these are the no-brainers that we have for RAM, but we need for SGX: MemTotal: xxxx kB // sgx_total_bytes (implemented here) MemFree: yyyy kB // sgx_free_bytes SwapTotal: zzzz kB // sgx_swapped_bytes So, at *least* three. I think we will eventually end up needing something more along the lines of a dozen. A new directory (as opposed to being in the nodeX/ "root") directory avoids cluttering the root with several "sgx_*" files. Place the new file in a new "nodeX/x86/" directory because SGX is highly x86-specific. It is very unlikely that any other architecture (or even non-Intel x86 vendor) will ever implement SGX. Using "sgx/" as opposed to "x86/" was also considered. But, there is a real chance this can get used for other arch-specific purposes. [ dhansen: rewrite changelog ] Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211116162116.93081-2-jarkko@kernel.org
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a495cbdf |
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26-Oct-2021 |
Tony Luck <tony.luck@intel.com> |
x86/sgx: Add SGX infrastructure to recover from poison Provide a recovery function sgx_memory_failure(). If the poison was consumed synchronously then send a SIGBUS. Note that the virtual address of the access is not included with the SIGBUS as is the case for poison outside of SGX enclaves. This doesn't matter as addresses of code/data inside an enclave is of little to no use to code executing outside the (now dead) enclave. Poison found in a free page results in the page being moved from the free list to the per-node poison page list. Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lkml.kernel.org/r/20211026220050.697075-5-tony.luck@intel.com
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992801ae |
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26-Oct-2021 |
Tony Luck <tony.luck@intel.com> |
x86/sgx: Initial poison handling for dirty and free pages A memory controller patrol scrubber can report poison in a page that isn't currently being used. Add "poison" field in the sgx_epc_page that can be set for an sgx_epc_page. Check for it: 1) When sanitizing dirty pages 2) When freeing epc pages Poison is a new field separated from flags to avoid having to make all updates to flags atomic, or integrate poison state changes into some other locking scheme to protect flags (Currently just sgx_reclaimer_lock which protects the SGX_EPC_PAGE_RECLAIMER_TRACKED bit in page->flags). In both cases place the poisoned page on a per-node list of poisoned epc pages to make sure it will not be reallocated. Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lkml.kernel.org/r/20211026220050.697075-4-tony.luck@intel.com
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40e0e784 |
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26-Oct-2021 |
Tony Luck <tony.luck@intel.com> |
x86/sgx: Add infrastructure to identify SGX EPC pages X86 machine check architecture reports a physical address when there is a memory error. Handling that error requires a method to determine whether the physical address reported is in any of the areas reserved for EPC pages by BIOS. SGX EPC pages do not have Linux "struct page" associated with them. Keep track of the mapping from ranges of EPC pages to the sections that contain them using an xarray. N.B. adds CONFIG_XARRAY_MULTI to the SGX dependecies. So "select" that in arch/x86/Kconfig for X86/SGX. Create a function arch_is_platform_page() that simply reports whether an address is an EPC page for use elsewhere in the kernel. The ACPI error injection code needs this function and is typically built as a module, so export it. Note that arch_is_platform_page() will be slower than other similar "what type is this page" functions that can simply check bits in the "struct page". If there is some future performance critical user of this function it may need to be implemented in a more efficient way. Note also that the current implementation of xarray allocates a few hundred kilobytes for this usage on a system with 4GB of SGX EPC memory configured. This isn't ideal, but worth it for the code simplicity. Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lkml.kernel.org/r/20211026220050.697075-3-tony.luck@intel.com
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d6d261bd |
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26-Oct-2021 |
Tony Luck <tony.luck@intel.com> |
x86/sgx: Add new sgx_epc_page flag bit to mark free pages SGX EPC pages go through the following life cycle: DIRTY ---> FREE ---> IN-USE --\ ^ | \-----------------/ Recovery action for poison for a DIRTY or FREE page is simple. Just make sure never to allocate the page. IN-USE pages need some extra handling. Add a new flag bit SGX_EPC_PAGE_IS_FREE that is set when a page is added to a free list and cleared when the page is allocated. Notes: 1) These transitions are made while holding the node->lock so that future code that checks the flags while holding the node->lock can be sure that if the SGX_EPC_PAGE_IS_FREE bit is set, then the page is on the free list. 2) Initially while the pages are on the dirty list the SGX_EPC_PAGE_IS_FREE bit is cleared. Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lkml.kernel.org/r/20211026220050.697075-2-tony.luck@intel.com
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ac5d272a |
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15-Nov-2021 |
Reinette Chatre <reinette.chatre@intel.com> |
x86/sgx: Fix free page accounting The SGX driver maintains a single global free page counter, sgx_nr_free_pages, that reflects the number of free pages available across all NUMA nodes. Correspondingly, a list of free pages is associated with each NUMA node and sgx_nr_free_pages is updated every time a page is added or removed from any of the free page lists. The main usage of sgx_nr_free_pages is by the reclaimer that runs when it (sgx_nr_free_pages) goes below a watermark to ensure that there are always some free pages available to, for example, support efficient page faults. With sgx_nr_free_pages accessed and modified from a few places it is essential to ensure that these accesses are done safely but this is not the case. sgx_nr_free_pages is read without any protection and updated with inconsistent protection by any one of the spin locks associated with the individual NUMA nodes. For example: CPU_A CPU_B ----- ----- spin_lock(&nodeA->lock); spin_lock(&nodeB->lock); ... ... sgx_nr_free_pages--; /* NOT SAFE */ sgx_nr_free_pages--; spin_unlock(&nodeA->lock); spin_unlock(&nodeB->lock); Since sgx_nr_free_pages may be protected by different spin locks while being modified from different CPUs, the following scenario is possible: CPU_A CPU_B ----- ----- {sgx_nr_free_pages = 100} spin_lock(&nodeA->lock); spin_lock(&nodeB->lock); sgx_nr_free_pages--; sgx_nr_free_pages--; /* LOAD sgx_nr_free_pages = 100 */ /* LOAD sgx_nr_free_pages = 100 */ /* sgx_nr_free_pages-- */ /* sgx_nr_free_pages-- */ /* STORE sgx_nr_free_pages = 99 */ /* STORE sgx_nr_free_pages = 99 */ spin_unlock(&nodeA->lock); spin_unlock(&nodeB->lock); In the above scenario, sgx_nr_free_pages is decremented from two CPUs but instead of sgx_nr_free_pages ending with a value that is two less than it started with, it was only decremented by one while the number of free pages were actually reduced by two. The consequence of sgx_nr_free_pages not being protected is that its value may not accurately reflect the actual number of free pages on the system, impacting the availability of free pages in support of many flows. The problematic scenario is when the reclaimer does not run because it believes there to be sufficient free pages while any attempt to allocate a page fails because there are no free pages available. In the SGX driver the reclaimer's watermark is only 32 pages so after encountering the above example scenario 32 times a user space hang is possible when there are no more free pages because of repeated page faults caused by no free pages made available. The following flow was encountered: asm_exc_page_fault ... sgx_vma_fault() sgx_encl_load_page() sgx_encl_eldu() // Encrypted page needs to be loaded from backing // storage into newly allocated SGX memory page sgx_alloc_epc_page() // Allocate a page of SGX memory __sgx_alloc_epc_page() // Fails, no free SGX memory ... if (sgx_should_reclaim(SGX_NR_LOW_PAGES)) // Wake reclaimer wake_up(&ksgxd_waitq); return -EBUSY; // Return -EBUSY giving reclaimer time to run return -EBUSY; return -EBUSY; return VM_FAULT_NOPAGE; The reclaimer is triggered in above flow with the following code: static bool sgx_should_reclaim(unsigned long watermark) { return sgx_nr_free_pages < watermark && !list_empty(&sgx_active_page_list); } In the problematic scenario there were no free pages available yet the value of sgx_nr_free_pages was above the watermark. The allocation of SGX memory thus always failed because of a lack of free pages while no free pages were made available because the reclaimer is never started because of sgx_nr_free_pages' incorrect value. The consequence was that user space kept encountering VM_FAULT_NOPAGE that caused the same address to be accessed repeatedly with the same result. Change the global free page counter to an atomic type that ensures simultaneous updates are done safely. While doing so, move the updating of the variable outside of the spin lock critical section to which it does not belong. Cc: stable@vger.kernel.org Fixes: 901ddbb9ecf5 ("x86/sgx: Add a basic NUMA allocation scheme to sgx_alloc_epc_page()") Suggested-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/a95a40743bbd3f795b465f30922dde7f1ea9e0eb.1637004094.git.reinette.chatre@intel.com
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ae40aaf6 |
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07-Apr-2021 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Do not update sgx_nr_free_pages in sgx_setup_epc_section() The commit in Fixes: changed the SGX EPC page sanitization to end up in sgx_free_epc_page() which puts clean and sanitized pages on the free list. This was done for the reason that it is best to keep the logic to assign available-for-use EPC pages to the correct NUMA lists in a single location. sgx_nr_free_pages is also incremented by sgx_free_epc_pages() but those pages which are being added there per EPC section do not belong to the free list yet because they haven't been sanitized yet - they land on the dirty list first and the sanitization happens later when ksgxd starts massaging them. So remove that addition there and have sgx_free_epc_page() do that solely. [ bp: Sanitize commit message too. ] Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list") Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210408092924.7032-1-jarkko@kernel.org
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b3754e5d |
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19-Mar-2021 |
Sean Christopherson <seanjc@google.com> |
x86/sgx: Move provisioning device creation out of SGX driver And extract sgx_set_attribute() out of sgx_ioc_enclave_provision() and export it as symbol for KVM to use. The provisioning key is sensitive. The SGX driver only allows to create an enclave which can access the provisioning key when the enclave creator has permission to open /dev/sgx_provision. It should apply to a VM as well, as the provisioning key is platform-specific, thus an unrestricted VM can also potentially compromise the provisioning key. Move the provisioning device creation out of sgx_drv_init() to sgx_init() as a preparation for adding SGX virtualization support, so that even if the SGX driver is not enabled due to flexible launch control not being available, SGX virtualization can still be enabled, and use it to restrict a VM's capability of being able to access the provisioning key. [ bp: Massage commit message. ] Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Acked-by: Dave Hansen <dave.hansen@intel.com> Link: https://lkml.kernel.org/r/0f4d044d621561f26d5f4ef73e8dc6cd18cc7e79.1616136308.git.kai.huang@intel.com
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73916b6a |
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19-Mar-2021 |
Kai Huang <kai.huang@intel.com> |
x86/sgx: Add helper to update SGX_LEPUBKEYHASHn MSRs Add a helper to update SGX_LEPUBKEYHASHn MSRs. SGX virtualization also needs to update those MSRs based on guest's "virtual" SGX_LEPUBKEYHASHn before EINIT from guest. Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Dave Hansen <dave.hansen@intel.com> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/dfb7cd39d4dd62ea27703b64afdd8bccb579f623.1616136308.git.kai.huang@intel.com
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faa7d3e6 |
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19-Mar-2021 |
Kai Huang <kai.huang@intel.com> |
x86/sgx: Initialize virtual EPC driver even when SGX driver is disabled Modify sgx_init() to always try to initialize the virtual EPC driver, even if the SGX driver is disabled. The SGX driver might be disabled if SGX Launch Control is in locked mode, or not supported in the hardware at all. This allows (non-Linux) guests that support non-LC configurations to use SGX. [ bp: De-silli-fy the test. ] Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Sean Christopherson <seanjc@google.com> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Acked-by: Dave Hansen <dave.hansen@intel.com> Link: https://lkml.kernel.org/r/d35d17a02bbf8feef83a536cec8b43746d4ea557.1616136308.git.kai.huang@intel.com
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b0c7459b |
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25-Mar-2021 |
Kai Huang <kai.huang@intel.com> |
x86/sgx: Wipe out EREMOVE from sgx_free_epc_page() EREMOVE takes a page and removes any association between that page and an enclave. It must be run on a page before it can be added into another enclave. Currently, EREMOVE is run as part of pages being freed into the SGX page allocator. It is not expected to fail, as it would indicate a use-after-free of EPC pages. Rather than add the page back to the pool of available EPC pages, the kernel intentionally leaks the page to avoid additional errors in the future. However, KVM does not track how guest pages are used, which means that SGX virtualization use of EREMOVE might fail. Specifically, it is legitimate that EREMOVE returns SGX_CHILD_PRESENT for EPC assigned to KVM guest, because KVM/kernel doesn't track SECS pages. To allow SGX/KVM to introduce a more permissive EREMOVE helper and to let the SGX virtualization code use the allocator directly, break out the EREMOVE call from the SGX page allocator. Rename the original sgx_free_epc_page() to sgx_encl_free_epc_page(), indicating that it is used to free an EPC page assigned to a host enclave. Replace sgx_free_epc_page() with sgx_encl_free_epc_page() in all call sites so there's no functional change. At the same time, improve the error message when EREMOVE fails, and add documentation to explain to the user what that failure means and to suggest to the user what to do when this bug happens in the case it happens. [ bp: Massage commit message, fix typos and sanitize text, simplify. ] Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/20210325093057.122834-1-kai.huang@intel.com
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901ddbb9 |
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17-Mar-2021 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Add a basic NUMA allocation scheme to sgx_alloc_epc_page() Background ========== SGX enclave memory is enumerated by the processor in contiguous physical ranges called Enclave Page Cache (EPC) sections. Currently, there is a free list per section, but allocations simply target the lowest-numbered sections. This is functional, but has no NUMA awareness. Fortunately, EPC sections are covered by entries in the ACPI SRAT table. These entries allow each EPC section to be associated with a NUMA node, just like normal RAM. Solution ======== Implement a NUMA-aware enclave page allocator. Mirror the buddy allocator and maintain a list of enclave pages for each NUMA node. Attempt to allocate enclave memory first from local nodes, then fall back to other nodes. Note that the fallback is not as sophisticated as the buddy allocator and is itself not aware of NUMA distances. When a node's free list is empty, it searches for the next-highest node with enclave pages (and will wrap if necessary). This could be improved in the future. Other ===== NUMA_KEEP_MEMINFO dependency is required for phys_to_target_node(). [ Kai Huang: Do not return NULL from __sgx_alloc_epc_page() because callers do not expect that and that leads to a NULL ptr deref. ] [ dhansen: Fix an uninitialized 'nid' variable in __sgx_alloc_epc_page() as Reported-by: kernel test robot <lkp@intel.com> to avoid any potential allocations from the wrong NUMA node or even premature allocation failures. ] Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://lore.kernel.org/lkml/158188326978.894464.217282995221175417.stgit@dwillia2-desk3.amr.corp.intel.com/ Link: https://lkml.kernel.org/r/20210319040602.178558-1-kai.huang@intel.com Link: https://lkml.kernel.org/r/20210318214933.29341-1-dave.hansen@intel.com Link: https://lkml.kernel.org/r/20210317235332.362001-2-jarkko.sakkinen@intel.com
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51ab30eb |
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17-Mar-2021 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list During normal runtime, the "ksgxd" daemon behaves like a version of kswapd just for SGX. But, before it starts acting like kswapd, its first job is to initialize enclave memory. Currently, the SGX boot code places each enclave page on a epc_section->init_laundry_list. Once it starts up, the ksgxd code walks over that list and populates the actual SGX page allocator. However, the per-section structures are going away to make way for the SGX NUMA allocator. There's also little need to have a per-section structure; the enclave pages are all treated identically, and they can be placed on the correct allocator list from metadata stored in the enclave page (struct sgx_epc_page) itself. Modify sgx_sanitize_section() to take a single page list instead of taking a section and deriving the list from there. Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://lkml.kernel.org/r/20210317235332.362001-1-jarkko.sakkinen@intel.com
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d9f6e12f |
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18-Mar-2021 |
Ingo Molnar <mingo@kernel.org> |
x86: Fix various typos in comments Fix ~144 single-word typos in arch/x86/ code comments. Doing this in a single commit should reduce the churn. Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: linux-kernel@vger.kernel.org
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31bf9288 |
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13-Jan-2021 |
Sami Tolvanen <samitolvanen@google.com> |
x86/sgx: Fix the return type of sgx_init() device_initcall() expects a function of type initcall_t, which returns an integer. Change the signature of sgx_init() to match. Fixes: e7e0545299d8c ("x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections") Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Darren Kenny <darren.kenny@oracle.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/20210113232311.277302-1-samitolvanen@google.com
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67655b57 |
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16-Nov-2020 |
Dave Hansen <dave.hansen@linux.intel.com> |
x86/sgx: Clarify 'laundry_list' locking Short Version: The SGX section->laundry_list structure is effectively thread-local, but declared next to some shared structures. Its semantics are clear as mud. Fix that. No functional changes. Compile tested only. Long Version: The SGX hardware keeps per-page metadata. This can provide things like permissions, integrity and replay protection. It also prevents things like having an enclave page mapped multiple times or shared between enclaves. But, that presents a problem for kexec()'d kernels (or any other kernel that does not run immediately after a hardware reset). This is because the last kernel may have been rude and forgotten to reset pages, which would trigger the "shared page" sanity check. To fix this, the SGX code "launders" the pages by running the EREMOVE instruction on all pages at boot. This is slow and can take a long time, so it is performed off in the SGX-specific ksgxd instead of being synchronous at boot. The init code hands the list of pages to launder in a per-SGX-section list: ->laundry_list. The only code to touch this list is the init code and ksgxd. This means that no locking is necessary for ->laundry_list. However, a lock is required for section->page_list, which is accessed while creating enclaves and by ksgxd. This lock (section->lock) is acquired by ksgxd while also processing ->laundry_list. It is easy to confuse the purpose of the locking as being for ->laundry_list and ->page_list. Rename ->laundry_list to ->init_laundry_list to make it clear that this is not normally used at runtime. Also add some comments clarifying the locking, and reorganize 'sgx_epc_section' to put 'lock' near the things it protects. Note: init_laundry_list is 128 bytes of wasted space at runtime. It could theoretically be dynamically allocated and then freed after the laundering process. But it would take nearly 128 bytes of extra instructions to do that. Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20201116222531.4834-1-dave.hansen@intel.com
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1728ab54 |
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12-Nov-2020 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Add a page reclaimer Just like normal RAM, there is a limited amount of enclave memory available and overcommitting it is a very valuable tool to reduce resource use. Introduce a simple reclaim mechanism for enclave pages. In contrast to normal page reclaim, the kernel cannot directly access enclave memory. To get around this, the SGX architecture provides a set of functions to help. Among other things, these functions copy enclave memory to and from normal memory, encrypting it and protecting its integrity in the process. Implement a page reclaimer by using these functions. Picks victim pages in LRU fashion from all the enclaves running in the system. A new kernel thread (ksgxswapd) reclaims pages in the background based on watermarks, similar to normal kswapd. All enclave pages can be reclaimed, architecturally. But, there are some limits to this, such as the special SECS metadata page which must be reclaimed last. The page version array (used to mitigate replaying old reclaimed pages) is also architecturally reclaimable, but not yet implemented. The end result is that the vast majority of enclave pages are currently reclaimable. Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Jethro Beekman <jethro@fortanix.com> Link: https://lkml.kernel.org/r/20201112220135.165028-22-jarkko@kernel.org
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3fe0778e |
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12-Nov-2020 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Add an SGX misc driver interface Intel(R) SGX is a new hardware functionality that can be used by applications to set aside private regions of code and data called enclaves. New hardware protects enclave code and data from outside access and modification. Add a driver that presents a device file and ioctl API to build and manage enclaves. [ bp: Small touchups, remove unused encl variable in sgx_encl_find() as Reported-by: kernel test robot <lkp@intel.com> ] Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Jethro Beekman <jethro@fortanix.com> Link: https://lkml.kernel.org/r/20201112220135.165028-12-jarkko@kernel.org
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d2285493 |
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12-Nov-2020 |
Jarkko Sakkinen <jarkko@kernel.org> |
x86/sgx: Add SGX page allocator functions Add functions for runtime allocation and free. This allocator and its algorithms are as simple as it gets. They do a linear search across all EPC sections and find the first free page. They are not NUMA-aware and only hand out individual pages. The SGX hardware does not support large pages, so something more complicated like a buddy allocator is unwarranted. The free function (sgx_free_epc_page()) implicitly calls ENCLS[EREMOVE], which returns the page to the uninitialized state. This ensures that the page is ready for use at the next allocation. Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Jethro Beekman <jethro@fortanix.com> Link: https://lkml.kernel.org/r/20201112220135.165028-10-jarkko@kernel.org
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e7e05452 |
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12-Nov-2020 |
Sean Christopherson <seanjc@google.com> |
x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Although carved out of normal DRAM, enclave memory is marked in the system memory map as reserved and is not managed by the core mm. There may be several regions spread across the system. Each contiguous region is called an Enclave Page Cache (EPC) section. EPC sections are enumerated via CPUID Enclave pages can only be accessed when they are mapped as part of an enclave, by a hardware thread running inside the enclave. Parse CPUID data, create metadata for EPC pages and populate a simple EPC page allocator. Although much smaller, ‘struct sgx_epc_page’ metadata is the SGX analog of the core mm ‘struct page’. Similar to how the core mm’s page->flags encode zone and NUMA information, embed the EPC section index to the first eight bits of sgx_epc_page->desc. This allows a quick reverse lookup from EPC page to EPC section. Existing client hardware supports only a single section, while upcoming server hardware will support at most eight sections. Thus, eight bits should be enough for long term needs. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Co-developed-by: Serge Ayoun <serge.ayoun@intel.com> Signed-off-by: Serge Ayoun <serge.ayoun@intel.com> Co-developed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Jethro Beekman <jethro@fortanix.com> Link: https://lkml.kernel.org/r/20201112220135.165028-6-jarkko@kernel.org
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