KVM: arm64: Fix host stage-2 PGD refcount

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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: 1025c8c0c6 ("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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Quentin Perret 2021-10-05 10:01:41 +01:00 • committed by Marc Zyngier

parent e840f42a49

commit 1d58a17ef5

3 changed files with 27 additions and 1 deletions

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1

arch/arm64/kvm/hyp/include/nvhe/gfp.h

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arch/arm64/kvm/hyp/nvhe/mem_protect.c

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arch/arm64/kvm/hyp/nvhe/page_alloc.c

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