KVM: x86/mmu: Trigger unprotect logic only on write-protection page faults

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Trigger KVM's various "unprotect gfn" paths if and only if the page fault
was a write to a write-protected gfn.  To do so, add a new page fault
return code, RET_PF_WRITE_PROTECTED, to explicitly and precisely track
such page faults.

If a page fault requires emulation for any MMIO (or any reason besides
write-protection), trying to unprotect the gfn is pointless and risks
putting the vCPU into an infinite loop.  E.g. KVM will put the vCPU into
an infinite loop if the vCPU manages to trigger MMIO on a page table walk.

Fixes: 147277540b ("kvm: svm: Add support for additional SVM NPF error codes")
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240831001538.336683-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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This commit is contained in:

Sean Christopherson 2024-08-30 17:15:18 -07:00

parent 4ececec19a

commit 989a84c93f

5 changed files with 50 additions and 37 deletions

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75

arch/x86/kvm/mmu/mmu.c

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arch/x86/kvm/mmu/mmu_internal.h

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arch/x86/kvm/mmu/mmutrace.h

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arch/x86/kvm/mmu/paging_tmpl.h

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arch/x86/kvm/mmu/tdp_mmu.c

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