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KVM: arm64: Reclaim faulting page from pKVM in spurious fault handler

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Host kernel accesses to pages that are inaccessible at stage-2 result in
the injection of a translation fault, which is fatal unless an exception
table fixup is registered for the faulting PC (e.g. for user access
routines). This is undesirable, since a get_user_pages() call could be
used to obtain a reference to a donated page and then a subsequent
access via a kernel mapping would lead to a panic().

Rework the spurious fault handler so that stage-2 faults injected back
into the host result in the target page being forcefully reclaimed when
no exception table fixup handler is registered.

Tested-by: Fuad Tabba <tabba@google.com>
Tested-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://patch.msgid.link/20260330144841.26181-27-will@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Will Deacon
2026-03-30 15:48:27 +01:00
committed by Marc Zyngier
parent 56080f53a6
commit 281a38ad29
3 changed files with 32 additions and 6 deletions
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12
arch/arm64/kvm/pkvm.c
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@@ -569,3 +569,15 @@ int pkvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size,
WARN_ON_ONCE(1);
return -EINVAL;
}
/*
* Forcefully reclaim a page from the guest, zeroing its contents and
* poisoning the stage-2 pte so that pages can no longer be mapped at
* the same IPA. The page remains pinned until the guest is destroyed.
*/
bool pkvm_force_reclaim_guest_page(phys_addr_t phys)
{
int ret = kvm_call_hyp_nvhe(__pkvm_force_reclaim_guest_page, phys);
return !ret || ret == -EAGAIN;
}