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The EL2 page allocator in protected mode maintains a per-pool max order
value to optimize allocations when the memory region it covers is small.
However, the max order value is currently under-estimated whenever the
number of pages in the region is a power of two. Fix the estimation.
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/20211208152300.2478542-2-qperret@google.com
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Some of the refcount manipulation helpers used at EL2 are instrumented
to catch a corrupted state, but not all of them are treated equally. Let's
make things more consistent by instrumenting hyp_page_ref_dec_and_test()
as well.
Acked-by: Will Deacon <will@kernel.org>
Suggested-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/20211005090155.734578-6-qperret@google.com
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The KVM page-table library refcounts the pages of concatenated stage-2
PGDs individually. However, when running KVM in protected mode, the
host's stage-2 PGD is currently managed by EL2 as a single high-order
compound page, which can cause the refcount of the tail pages to reach 0
when they shouldn't, hence corrupting the page-table.
Fix this by introducing a new hyp_split_page() helper in the EL2 page
allocator (matching the kernel's split_page() function), and make use of
it from host_s2_zalloc_pages_exact().
Fixes: 1025c8c0c6ac ("KVM: arm64: Wrap the host with a stage 2")
Acked-by: Will Deacon <will@kernel.org>
Suggested-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/20211005090155.734578-5-qperret@google.com
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The hyp_page refcount is currently encoded on 4 bytes even though we
never need to count that many objects in a page. Make it 2 bytes to save
some space in the vmemmap.
As overflows are more likely to happen as well, make sure to catch those
with a BUG in the increment function.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-8-qperret@google.com
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The hyp_page order is currently encoded on 4 bytes even though it is
guaranteed to be smaller than this. Make it 2 bytes to reduce the hyp
vmemmap overhead.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-7-qperret@google.com
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Each struct hyp_page currently contains a pointer to a hyp_pool struct
where the page should be freed if its refcount reaches 0. However, this
information can always be inferred from the context in the EL2 code, so
drop the pointer to save a few bytes in the vmemmap.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-6-qperret@google.com
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The list_head member of struct hyp_page is only needed when the page is
attached to a free-list, which by definition implies the page is free.
As such, nothing prevents us from using the page itself to store the
list_head, hence reducing the size of the vmemmap.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-4-qperret@google.com
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The hyp buddy allocator currently checks the struct hyp_page list node
to see if a page is available for allocation or not when trying to
coalesce memory. Now that decrementing the refcount and attaching to
the buddy tree is done in the same critical section, we can rely on the
refcount of the buddy page to be in sync, which allows to replace the
list node check by a refcount check. This will ease removing the list
node from struct hyp_page later on.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-3-qperret@google.com
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The hyp_page refcount helpers currently rely on the hyp_pool lock for
serialization. However, this means the refcounts can't be changed from
the buddy allocator core as it already holds the lock, which means pages
have to go through odd transient states.
For example, when a page is freed, its refcount is set to 0, and the
lock is transiently released before the page can be attached to a free
list in the buddy tree. This is currently harmless as the allocator
checks the list node of each page to see if it is available for
allocation or not, but it means the page refcount can't be trusted to
represent the state of the page even if the pool lock is held.
In order to fix this, remove the pool locking from the refcount helpers,
and move all the logic to the buddy allocator. This will simplify the
removal of the list node from struct hyp_page in a later patch.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-2-qperret@google.com
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When memory protection is enabled, the hyp code will require a basic
form of memory management in order to allocate and free memory pages at
EL2. This is needed for various use-cases, including the creation of hyp
mappings or the allocation of stage 2 page tables.
To address these use-case, introduce a simple memory allocator in the
hyp code. The allocator is designed as a conventional 'buddy allocator',
working with a page granularity. It allows to allocate and free
physically contiguous pages from memory 'pools', with a guaranteed order
alignment in the PA space. Each page in a memory pool is associated
with a struct hyp_page which holds the page's metadata, including its
refcount, as well as its current order, hence mimicking the kernel's
buddy system in the GFP infrastructure. The hyp_page metadata are made
accessible through a hyp_vmemmap, following the concept of
SPARSE_VMEMMAP in the kernel.
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/20210319100146.1149909-13-qperret@google.com
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