KVM: arm64: Remove size-order align in the nVHE hyp private VA range

commit f922c13e778d ("KVM: arm64: Introduce
pkvm_alloc_private_va_range()") and commit 92abe0f81e13 ("KVM: arm64:
Introduce hyp_alloc_private_va_range()") added an alignment for the
start address of any allocation into the nVHE hypervisor private VA
range.

This alignment (order of the size of the allocation) intends to enable
efficient stack verification (if the PAGE_SHIFT bit is zero, the stack
pointer is on the guard page and a stack overflow occurred).

But this is only necessary for stack allocation and can waste a lot of
VA space. So instead make stack-specific functions, handling the guard
page requirements, while other users (e.g. fixmap) will only get page
alignment.

Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230811112037.1147863-1-vdonnefort@google.com

KVM: arm64: Add per-cpu fixmap infrastructure at EL2

Mapping pages in a guest page-table from within the pKVM hypervisor at
EL2 may require cache maintenance to ensure that the initialised page
contents is visible even to non-cacheable (e.g. MMU-off) accesses from
the guest.

In preparation for performing this maintenance at EL2, introduce a
per-vCPU fixmap which allows the pKVM hypervisor to map guest pages
temporarily into its stage-1 page-table for the purposes of cache
maintenance and, in future, poisoning on the reclaim path. The use of a
fixmap avoids the need for memory allocation or locking on the map()
path.

Tested-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Co-developed-by: Will Deacon <will@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221110190259.26861-15-will@kernel.org

KVM: arm64: Back the hypervisor 'struct hyp_page' array for all memory

The EL2 'vmemmap' array in nVHE Protected mode is currently very sparse:
only memory pages owned by the hypervisor itself have a matching 'struct
hyp_page'. However, as the size of this struct has been reduced
significantly since its introduction, it appears that we can now afford
to back the vmemmap for all of memory.

Having an easily accessible 'struct hyp_page' for every physical page in
memory provides the hypervisor with a simple mechanism to store metadata
(e.g. a refcount) that wouldn't otherwise fit in the very limited number
of software bits available in the host stage-2 page-table entries. This
will be used in subsequent patches when pinning host memory pages for
use by the hypervisor at EL2.

Tested-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221110190259.26861-4-will@kernel.org

KVM: arm64: Introduce pkvm_alloc_private_va_range()

pkvm_hyp_alloc_private_va_range() can be used to reserve private VA ranges
in the pKVM nVHE hypervisor. Allocations are aligned based on the order of
the requested size.

This will be used to implement stack guard pages for pKVM nVHE hypervisor
(in a subsequent patch in the series).

Credits to Quentin Perret <qperret@google.com> for the idea of moving
private VA allocation out of __pkvm_create_private_mapping()

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220420214317.3303360-3-kaleshsingh@google.com

KVM: arm64: Make __io_map_base static

The __io_map_base variable is used at EL2 to track the end of the
hypervisor's "private" VA range in nVHE protected mode. However it
doesn't need to be used outside of mm.c, so let's make it static to keep
all the hyp VA allocation logic in one place.

Signed-off-by: Quentin Perret <qperret@google.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211208152300.2478542-5-qperret@google.com

KVM: arm64: Make the hyp memory pool static

The hyp memory pool struct is sized to fit exactly the needs of the
hypervisor stage-1 page-table allocator, so it is important it is not
used for anything else. As it is currently used only from setup.c,
reduce its visibility by marking it static.

Signed-off-by: Quentin Perret <qperret@google.com>
Reviewed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211208152300.2478542-4-qperret@google.com

KVM: arm64: Move host EL1 code out of hyp/ directory

kvm/hyp/reserved_mem.c contains host code executing at EL1 and is not
linked into the hypervisor object. Move the file into kvm/pkvm.c and
rework the headers so that the definitions shared between the host and
the hypervisor live in asm/kvm_pkvm.h.

Signed-off-by: Will Deacon <will@kernel.org>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211202171048.26924-4-will@kernel.org

KVM: arm64: Make __pkvm_create_mappings static

The __pkvm_create_mappings() function is no longer used outside of
nvhe/mm.c, make it static.

Signed-off-by: Quentin Perret <qperret@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-22-qperret@google.com

KVM: arm64: Refactor protected nVHE stage-1 locking

Refactor the hypervisor stage-1 locking in nVHE protected mode to expose
a new pkvm_create_mappings_locked() function. This will be used in later
patches to allow walking and changing the hypervisor stage-1 without
releasing the lock.

Signed-off-by: Quentin Perret <qperret@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-20-qperret@google.com

KVM: arm64: Unify MMIO and mem host stage-2 pools

We currently maintain two separate memory pools for the host stage-2,
one for pages used in the page-table when mapping memory regions, and
the other to map MMIO regions. The former is large enough to map all of
memory with page granularity and the latter can cover an arbitrary
portion of IPA space, but allows to 'recycle' pages.

However, this split makes accounting difficult to manage as pages at
intermediate levels of the page-table may be used to map both memory and
MMIO regions. Simplify the scheme by merging both pools into one. This
means we can now hit the -ENOMEM case in the memory abort path, but
we're still guaranteed forward-progress in the worst case by unmapping
MMIO regions. On the plus side this also means we can usually map a lot
more MMIO space at once if memory ranges happen to be mapped with block
mappings.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-5-qperret@google.com

KVM: arm64: Reserve memory for host stage 2

Extend the memory pool allocated for the hypervisor to include enough
pages to map all of memory at page granularity for the host stage 2.
While at it, also reserve some memory for device mappings.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-27-qperret@google.com

KVM: arm64: Prepare the creation of s1 mappings at EL2

When memory protection is enabled, the EL2 code needs the ability to
create and manage its own page-table. To do so, introduce a new set of
hypercalls to bootstrap a memory management system at EL2.

This leads to the following boot flow in nVHE Protected mode:

1. the host allocates memory for the hypervisor very early on, using
the memblock API;

2. the host creates a set of stage 1 page-table for EL2, installs the
EL2 vectors, and issues the __pkvm_init hypercall;

3. during __pkvm_init, the hypervisor re-creates its stage 1 page-table
and stores it in the memory pool provided by the host;

4. the hypervisor then extends its stage 1 mappings to include a
vmemmap in the EL2 VA space, hence allowing to use the buddy
allocator introduced in a previous patch;

5. the hypervisor jumps back in the idmap page, switches from the
host-provided page-table to the new one, and wraps up its
initialization by enabling the new allocator, before returning to
the host.

6. the host can free the now unused page-table created for EL2, and
will now need to issue hypercalls to make changes to the EL2 stage 1
mappings instead of modifying them directly.

Note that for the sake of simplifying the review, this patch focuses on
the hypervisor side of things. In other words, this only implements the
new hypercalls, but does not make use of them from the host yet. The
host-side changes will follow in a subsequent patch.

Credits to Will for __pkvm_init_switch_pgd.

Acked-by: Will Deacon <will@kernel.org>
Co-authored-by: Will Deacon <will@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-18-qperret@google.com