xen/xenbus: document will_handle argument for xenbus_watch_path()

Commit 2e85d32b1c86 ("xen/xenbus: Add 'will_handle' callback support in
xenbus_watch_path()") added will_handle argument to xenbus_watch_path()
and its wrapper, xenbus_watch_pathfmt(), but didn't document it on the
kerneldoc comments of the function. This is causing warnings that
reported by kernel test robot. Add the documentation to fix it.

Fixes: 2e85d32b1c86 ("xen/xenbus: Add 'will_handle' callback support in xenbus_watch_path()")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202401121154.FI8jDGun-lkp@intel.com/
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20240112185903.83737-1-sj@kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: client: fix kernel-doc comments

Correct function kernel-doc notation to prevent warnings from
scripts/kernel-doc.

xenbus_client.c:134: warning: No description found for return value of 'xenbus_watch_path'
xenbus_client.c:177: warning: No description found for return value of 'xenbus_watch_pathfmt'
xenbus_client.c:258: warning: missing initial short description on line:
* xenbus_switch_state
xenbus_client.c:267: warning: No description found for return value of 'xenbus_switch_state'
xenbus_client.c:308: warning: missing initial short description on line:
* xenbus_dev_error
xenbus_client.c:327: warning: missing initial short description on line:
* xenbus_dev_fatal
xenbus_client.c:350: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* Equivalent to xenbus_dev_fatal(dev, err, fmt, args), but helps
xenbus_client.c:457: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* Allocate an event channel for the given xenbus_device, assigning the newly
xenbus_client.c:486: warning: expecting prototype for Free an existing event channel. Returns 0 on success or(). Prototype was for xenbus_free_evtchn() instead
xenbus_client.c:502: warning: missing initial short description on line:
* xenbus_map_ring_valloc
xenbus_client.c:517: warning: No description found for return value of 'xenbus_map_ring_valloc'
xenbus_client.c:602: warning: missing initial short description on line:
* xenbus_unmap_ring
xenbus_client.c:614: warning: No description found for return value of 'xenbus_unmap_ring'
xenbus_client.c:715: warning: missing initial short description on line:
* xenbus_unmap_ring_vfree
xenbus_client.c:727: warning: No description found for return value of 'xenbus_unmap_ring_vfree'
xenbus_client.c:919: warning: missing initial short description on line:
* xenbus_read_driver_state
xenbus_client.c:926: warning: No description found for return value of 'xenbus_read_driver_state'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20231206181724.27767-1-rdunlap@infradead.org
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: fix xenbus_setup_ring()

Commit 4573240f0764 ("xen/xenbus: eliminate xenbus_grant_ring()")
introduced an error for initialization of multi-page rings.

Cc: stable@vger.kernel.org
Fixes: 4573240f0764 ("xen/xenbus: eliminate xenbus_grant_ring()")
Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen: switch gnttab_end_foreign_access() to take a struct page pointer

Instead of a virtual kernel address use a pointer of the associated
struct page as second parameter of gnttab_end_foreign_access().

Most users have that pointer available already and are creating the
virtual address from it, risking problems in case the memory is
located in highmem.

gnttab_end_foreign_access() itself won't need to get the struct page
from the address again.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: eliminate xenbus_grant_ring()

There is no external user of xenbus_grant_ring() left, so merge it into
the only caller xenbus_setup_ring().

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: add xenbus_setup_ring() service function

Most PV device frontends share very similar code for setting up shared
ring buffers:

- allocate page(s)
- init the ring admin data
- give the backend access to the ring via grants

Tearing down the ring requires similar actions in all frontends again:

- remove grants
- free the page(s)

Provide service functions xenbus_setup_ring() and xenbus_teardown_ring()
for that purpose.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: don't let xenbus_grant_ring() remove grants in error case

Letting xenbus_grant_ring() tear down grants in the error case is
problematic, as the other side could already have used these grants.
Calling gnttab_end_foreign_access_ref() without checking success is
resulting in an unclear situation for any caller of xenbus_grant_ring()
as in the error case the memory pages of the ring page might be
partially mapped. Freeing them would risk unwanted foreign access to
them, while not freeing them would leak memory.

In order to remove the need to undo any gnttab_grant_foreign_access()
calls, use gnttab_alloc_grant_references() to make sure no further
error can occur in the loop granting access to the ring pages.

It should be noted that this way of handling removes leaking of
grant entries in the error case, too.

This is CVE-2022-23040 / part of XSA-396.

Reported-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

drivers/xen/xenbus/xenbus_client.c: fix bugon.cocci warnings

Use BUG_ON instead of a if condition followed by BUG.

Generated by: scripts/coccinelle/misc/bugon.cocci

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
Reviewed-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210825062451.69998-1-deng.changcheng@zte.com.cn
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: Add 'will_handle' callback support in xenbus_watch_path()

Some code does not directly make 'xenbus_watch' object and call
'register_xenbus_watch()' but use 'xenbus_watch_path()' instead. This
commit adds support of 'will_handle' callback in the
'xenbus_watch_path()' and it's wrapper, 'xenbus_watch_pathfmt()'.

This is part of XSA-349

Cc: stable@vger.kernel.org
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reported-by: Michael Kurth <mku@amazon.de>
Reported-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: Allow watches discard events before queueing

If handling logics of watch events are slower than the events enqueue
logic and the events can be created from the guests, the guests could
trigger memory pressure by intensively inducing the events, because it
will create a huge number of pending events that exhausting the memory.

Fortunately, some watch events could be ignored, depending on its
handler callback. For example, if the callback has interest in only one
single path, the watch wouldn't want multiple pending events. Or, some
watches could ignore events to same path.

To let such watches to volutarily help avoiding the memory pressure
situation, this commit introduces new watch callback, 'will_handle'. If
it is not NULL, it will be called for each new event just before
enqueuing it. Then, if the callback returns false, the event will be
discarded. No watch is using the callback for now, though.

This is part of XSA-349

Cc: stable@vger.kernel.org
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reported-by: Michael Kurth <mku@amazon.de>
Reported-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: use apply_to_page_range directly in xenbus_map_ring_pv

Replacing alloc_vm_area with get_vm_area_caller + apply_page_range allows
to fill put the phys_addr values directly instead of doing another loop
over all addresses.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Link: https://lkml.kernel.org/r/20201002122204.1534411-10-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

xen: add helpers to allocate unpopulated memory

To be used in order to create foreign mappings. This is based on the
ZONE_DEVICE facility which is used by persistent memory devices in
order to create struct pages and kernel virtual mappings for the IOMEM
areas of such devices. Note that on kernels without support for
ZONE_DEVICE Xen will fallback to use ballooned pages in order to
create foreign mappings.

The newly added helpers use the same parameters as the existing
{alloc/free}_xenballooned_pages functions, which allows for in-place
replacement of the callers. Once a memory region has been added to be
used as scratch mapping space it will no longer be released, and pages
returned are kept in a linked list. This allows to have a buffer of
pages and prevents resorting to frequent additions and removals of
regions.

If enabled (because ZONE_DEVICE is supported) the usage of the new
functionality untangles Xen balloon and RAM hotplug from the usage of
unpopulated physical memory ranges to map foreign pages, which is the
correct thing to do in order to avoid mappings of foreign pages depend
on memory hotplug.

Note the driver is currently not enabled on Arm platforms because it
would interfere with the identity mapping required on some platforms.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20200901083326.21264-4-roger.pau@citrix.com
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: Fix granting of vmalloc'd memory

On some architectures (like ARM), virt_to_gfn cannot be used for
vmalloc'd memory because of its reliance on virt_to_phys. This patch
introduces a check for vmalloc'd addresses and obtains the PFN using
vmalloc_to_pfn in that case.

Signed-off-by: Simon Leiner <simon@leiner.me>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20200825093153.35500-1-simon@leiner.me
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: Fix a double free in xenbus_map_ring_pv()

When there is an error the caller frees "info->node" so the free here
will result in a double free. We should just delete first kfree().

Fixes: 3848e4e0a32a ("xen/xenbus: avoid large structs and arrays on the stack")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200710113610.GA92345@mwanda
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/xenbus: let xenbus_map_ring_valloc() return errno values only

Today xenbus_map_ring_valloc() can return either a negative errno
value (-ENOMEM or -EINVAL) or a grant status value. This is a mess as
e.g -ENOMEM and GNTST_eagain have the same numeric value.

Fix that by turning all grant mapping errors into -ENOENT. This is
no problem as all callers of xenbus_map_ring_valloc() only use the
return value to print an error message, and in case of mapping errors
the grant status value has already been printed by __xenbus_map_ring()
before.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200701121638.19840-3-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/xenbus: avoid large structs and arrays on the stack

xenbus_map_ring_valloc() and its sub-functions are putting quite large
structs and arrays on the stack. This is problematic at runtime, but
might also result in build failures (e.g. with clang due to the option
-Werror,-Wframe-larger-than=... used).

Fix that by moving most of the data from the stack into a dynamically
allocated struct. Performance is no issue here, as
xenbus_map_ring_valloc() is used only when adding a new PV device to
a backend driver.

While at it move some duplicated code from pv/hvm specific mapping
functions to the single caller.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200701121638.19840-2-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/xenbus: ensure xenbus_map_ring_valloc() returns proper grant status

xenbus_map_ring_valloc() maps a ring page and returns the status of the
used grant (0 meaning success).

There are Xen hypervisors which might return the value 1 for the status
of a failed grant mapping due to a bug. Some callers of
xenbus_map_ring_valloc() test for errors by testing the returned status
to be less than zero, resulting in no error detected and crashing later
due to a not available ring page.

Set the return value of xenbus_map_ring_valloc() to GNTST_general_error
in case the grant status reported by Xen is greater than zero.

This is part of XSA-316.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>
Link: https://lore.kernel.org/r/20200326080358.1018-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

xen: Use evtchn_type_t as a type for event channels

Make event channel functions pass event channel port using
evtchn_port_t type. It eliminates signed <-> unsigned conversion.

Signed-off-by: Yan Yankovskyi <yyankovskyi@gmail.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200323152343.GA28422@kbp1-lhp-F74019
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/xenbus: remove unused xenbus_map_ring()

xenbus_map_ring() is used nowhere in the tree, remove it.
xenbus_unmap_ring() is used only locally, so make it static and move it
up.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen: drop writing error messages to xenstore

xenbus_va_dev_error() will try to write error messages to Xenstore
under the error/<dev-name>/error node (with <dev-name> something like
"device/vbd/51872"). This will fail normally and another message
about this failure is added to dmesg.

I believe this is a remnant from very ancient times, as it was added
in the first pvops rush of commits in 2007.

So remove the additional message when writing to Xenstore failed as
a minimum step.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracel.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen: don't compile pv-specific parts if XEN_PV isn't configured

xenbus_client.c contains some functions specific for pv guests.
Enclose them with #ifdef CONFIG_XEN_PV to avoid compiling them when
they are not needed (e.g. on ARM).

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen: modify xenstore watch event interface

Today a Xenstore watch event is delivered via a callback function
declared as:

void (*callback)(struct xenbus_watch *,
const char **vec, unsigned int len);

As all watch events only ever come with two parameters (path and token)
changing the prototype to:

void (*callback)(struct xenbus_watch *,
const char *path, const char *token);

is the natural thing to do.

Apply this change and adapt all users.

Cc: konrad.wilk@oracle.com
Cc: roger.pau@citrix.com
Cc: wei.liu2@citrix.com
Cc: paul.durrant@citrix.com
Cc: netdev@vger.kernel.org

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen: clean up xenbus internal headers

The xenbus driver has an awful mixture of internally and globally
visible headers: some of the internally used only stuff is defined in
the global header include/xen/xenbus.h while some stuff defined in
internal headers is used by other drivers, too.

Clean this up by moving the externally used symbols to
include/xen/xenbus.h and the symbols used internally only to a new
header drivers/xen/xenbus/xenbus.h replacing xenbus_comms.h and
xenbus_probe.h

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xenbus: Neaten xenbus_va_dev_error

This function error patch can be simplified, so do so.

Remove fail: label and somewhat obfuscating, used once "error_path"
function.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xenbus: Support multiple grants ring with 64KB

The PV ring may use multiple grants and expect them to be mapped
contiguously in the virtual memory.

Although, the current code is relying on a Linux page will be mapped to
a single grant. On build where Linux is using a different page size than
the grant (i.e other than 4KB), the grant will always be mapped on the
first 4KB of each Linux page which make the final ring not contiguous in
the memory.

This can be fixed by mapping multiple grant in a same Linux page.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: Rename *RING_PAGE* to *RING_GRANT*

Linux may use a different page size than the size of grant. So make
clear that the order is actually in number of grant.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: Use Xen page definition

All the ring (xenstore, and PV rings) are always based on the page
granularity of Xen.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/balloon: make alloc_xenballoon_pages() always allocate low pages

All users of alloc_xenballoon_pages() wanted low memory pages, so
remove the option for high memory.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

xen: Use correctly the Xen memory terminologies

Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
is meant, I suspect this is because the first support for Xen was for
PV. This resulted in some misimplementation of helpers on ARM and
confused developers about the expected behavior.

For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
Although, if we look at the implementation on x86, it's returning a GFN.

For clarity and avoid new confusion, replace any reference to mfn with
gfn in any helpers used by PV drivers. The x86 code will still keep some
reference of pfn_to_mfn which may be used by all kind of guests
No changes as been made in the hypercall field, even
though they may be invalid, in order to keep the same as the defintion
in xen repo.

Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a
name to close to the KVM function gfn_to_page.

Take also the opportunity to simplify simple construction such
as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up
will come in follow-up patches.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

The commit ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d "xenbus_client:
Extend interface to support multi-page ring" removes the call to
free_xenballooned_pages() in xenbus_unmap_ring_vfree_hvm(), leaking a
page for every shared ring.

Only with backends running in HVM domains were affected.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: client: Fix call of virt_to_mfn in xenbus_grant_ring

virt_to_mfn should take a void* rather an unsigned long. While it
doesn't really matter now, it would throw a compiler warning later when
virt_to_mfn will enforce the type.

At the same time, avoid to compute new virtual address every time in the
loop and directly increment the parameter as we don't use it later.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen: Include xen/page.h rather than asm/xen/page.h

Using xen/page.h will be necessary later for using common xen page
helpers.

As xen/page.h already include asm/xen/page.h, always use the later.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: netdev@vger.kernel.org
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xenbus_client: Extend interface to support multi-page ring

Originally Xen PV drivers only use single-page ring to pass along
information. This might limit the throughput between frontend and
backend.

The patch extends Xenbus driver to support multi-page ring, which in
general should improve throughput if ring is the bottleneck. Changes to
various frontend / backend to adapt to the new interface are also
included.

Affected Xen drivers:
* blkfront/back
* netfront/back
* pcifront/back
* scsifront/back
* vtpmfront

The interface is documented, as before, in xenbus_client.c.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: Remove BUG_ON() when error string trucated

xenbus_va_dev_error() is for printing error, so when error string is
too long to be truncated, need not BUG_ON(), still return truncation
string is OK.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: Correct the comments for xenbus_grant_ring()

A grant reference (which is a positive number) can indicate success, so
the original comments need be improved.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

xen/xenbus: remove unused xenbus_bind_evtchn()

xenbus_bind_evtchn() has no callers so remove it.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/pvh: Piggyback on PVHVM XenBus.

PVH is a PV guest with a twist - there are certain things
that work in it like HVM and some like PV. For the XenBus
mechanism we want to use the PVHVM mechanism.

Signed-off-by: Mukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

xenbus_client.c: correct exit path for xenbus_map_ring_valloc_hvm

Apparently we should not free page that has not been allocated.
This is b/c alloc_xenballooned_pages will take care of freeing
the page on its own.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xenbus: fix compile failure on ARM with Xen enabled

Adding an include of linux/mm.h resolves this:
drivers/xen/xenbus/xenbus_client.c: In function ‘xenbus_map_ring_valloc_hvm’:
drivers/xen/xenbus/xenbus_client.c:532:66: error: implicit declaration of function ‘page_to_section’ [-Werror=implicit-function-declaration]

CC: stable@vger.kernel.org
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/gndev: Xen backend support for paged out grant targets V4.

Since Xen-4.2, hvm domains may have portions of their memory paged out. When a
foreign domain (such as dom0) attempts to map these frames, the map will
initially fail. The hypervisor returns a suitable errno, and kicks an
asynchronous page-in operation carried out by a helper. The foreign domain is
expected to retry the mapping operation until it eventually succeeds. The
foreign domain is not put to sleep because itself could be the one running the
pager assist (typical scenario for dom0).

This patch adds support for this mechanism for backend drivers using grant
mapping and copying operations. Specifically, this covers the blkback and
gntdev drivers (which map foreign grants), and the netback driver (which copies
foreign grants).

* Add a retry method for grants that fail with GNTST_eagain (i.e. because the
target foreign frame is paged out).
* Insert hooks with appropriate wrappers in the aforementioned drivers.

The retry loop is only invoked if the grant operation status is GNTST_eagain.
It guarantees to leave a new status code different from GNTST_eagain. Any other
status code results in identical code execution as before.

The retry loop performs 256 attempts with increasing time intervals through a
32 second period. It uses msleep to yield while waiting for the next retry.

V2 after feedback from David Vrabel:
* Explicit MAX_DELAY instead of wrap-around delay into zero
* Abstract GNTST_eagain check into core grant table code for netback module.

V3 after feedback from Ian Campbell:
* Add placeholder in array of grant table error descriptions for unrelated
error code we jump over.
* Eliminate single map and retry macro in favor of a generic batch flavor.
* Some renaming.
* Bury most implementation in grant_table.c, cleaner interface.

V4 rebased on top of sync of Xen grant table interface headers.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[v5: Fixed whitespace issues]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xenbus: address compiler warnings

- casting pointers to integer types of different size is being warned on
- an uninitialized variable warning occurred on certain gcc versions

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xenbus: Use grant-table wrapper functions

For xenbus_{map,unmap}_ring to work on HVM, the grant table operations
must be set up using the gnttab_set_{map,unmap}_op functions instead of
directly populating the fields of gnttab_map_grant_ref. These functions
simply populate the structure on paravirtualized Xen; however, on HVM
they must call __pa() on vaddr when populating op->host_addr because the
hypervisor cannot directly interpret guest-virtual addresses.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
[v1: Fixed cleanpatch error]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xenbus: Support HVM backends

Add HVM implementations of xenbus_(map,unmap)_ring_v(alloc,free) so
that ring mappings can be done without using GNTMAP_contains_pte which
is not supported on HVM. This also removes the need to use vmlist_lock
on PV by tracking the allocated xenbus rings.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
[v1: Fix compile error when XENBUS_FRONTEND is defined as module]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen: map foreign pages for shared rings by updating the PTEs directly

When mapping a foreign page with xenbus_map_ring_valloc() with the
GNTTABOP_map_grant_ref hypercall, set the GNTMAP_contains_pte flag and
pass a pointer to the PTE (in init_mm).

After the page is mapped, the usual fault mechanism can be used to
update additional MMs. This allows the vmalloc_sync_all() to be
removed from alloc_vm_area().

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
[v1: Squashed fix by Michal for no-mmu case]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

xen: Add export.h for THIS_MODULE/EXPORT_SYMBOL to various xen users.

Things like THIS_MODULE and EXPORT_SYMBOL were simply everywhere
because module.h was also everywhere. But we are fixing the latter.
So we need to call out the real users in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

xen: use generic functions instead of xen_{alloc, free}_vm_area()

Replace calls to the Xen-specific xen_alloc_vm_area() and
xen_free_vm_area() functions with the generic equivalent
(alloc_vm_area() and free_vm_area()).

On x86, these were identical already.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xenbus: Xen paravirtualised PCI hotplug support.

The Xen PCI front driver adds two new states that are utilizez
for PCI hotplug support. This is a patch pulled from the
linux-2.6-xen-sparse tree.

Signed-off-by: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Yosuke Iwamatsu <y-iwamatsu@ab.jp.nec.com>

xenbus: Make xenbus_switch_state transactional

According to the comments, this was how it's been done years ago, but
apparently took an xbt pointer from elsewhere back then. The code was
removed because of consistency issues: cancellation wont't roll back
the saved xbdev->state.

Still, unsolicited writes to the state field remain an issue,
especially if device shutdown takes thread synchronization, and subtle
races cause accidental recreation of the device node.

Fixed by reintroducing the transaction. An internal one is sufficient,
so the xbdev->state value remains consistent.

Also fixes the original hack to prevent infinite recursion. Instead of
bailing out on the first attempt to switch to Closing, checks call
depth now.

Signed-off-by: Daniel Stodden <daniel.stodden@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.

2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).

* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

drivers/xen/xenbus/xenbus_client.c: cleanup kerneldoc

no argument named @xbt in xenbus_switch_state(), remove it.

Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

xen: Avoid allocations causing swap activity on the resume path

Avoid allocations causing swap activity on the resume path by
preventing the allocations from doing IO and allowing them
to access the emergency pools.

These paths are used when a frontend device is trying to connect
to its backend driver over Xenbus. These reconnections are triggered
on demand by IO, so by definition there is already IO underway,
and further IO would naturally deadlock. On resume, this path
is triggered when the running system tries to continue using its
devices. If it cannot then the resume will fail; to try to avoid this
we let it dip into the emergency pools.

[ linux-2.6.18-xen changesets e8b49cfbdac, fdb998e79aba ]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

xen: replace callers of alloc_vm_area()/free_vm_area() with xen_ prefixed one

Don't use alloc_vm_area()/free_vm_area() directly, instead define
xen_alloc_vm_area()/xen_free_vm_area() and use them.

alloc_vm_area()/free_vm_area() are used to allocate/free area which
are for grant table mapping. Xen/x86 grant table is based on virtual
address so that alloc_vm_area()/free_vm_area() are suitable.
On the other hand Xen/ia64 (and Xen/powerpc) grant table is based on
pseudo physical address (guest physical address) so that allocation
should be done differently.
The original version of xenified Linux/IA64 have its own
allocate_vm_area()/free_vm_area() definitions which don't allocate vm area
contradictory to those names.
Now vanilla Linux already has its definitions so that it's impossible
to have IA64 definitions of allocate_vm_area()/free_vm_area().
Instead introduce xen_allocate_vm_area()/xen_free_vm_area() and use them.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

xen: add the Xenbus sysfs and virtual device hotplug driver

This communicates with the machine control software via a registry
residing in a controlling virtual machine. This allows dynamic
creation, destruction and modification of virtual device
configurations (network devices, block devices and CPUS, to name some
examples).

[ Greg, would you mind giving this a review? Thanks -J ]

Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Greg KH <greg@kroah.com>