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Revert "KVM: SVM: avoid infinite loop on NPF from bad address"

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commit 31c2558569 upstream.

Revert a completely broken check on an "invalid" RIP in SVM's workaround
for the DecodeAssists SMAP errata.  kvm_vcpu_gfn_to_memslot() obviously
expects a gfn, i.e. operates in the guest physical address space, whereas
RIP is a virtual (not even linear) address.  The "fix" worked for the
problematic KVM selftest because the test identity mapped RIP.

Fully revert the hack instead of trying to translate RIP to a GPA, as the
non-SEV case is now handled earlier, and KVM cannot access guest page
tables to translate RIP.

This reverts commit e72436bc3a.

Fixes: e72436bc3a ("KVM: SVM: avoid infinite loop on NPF from bad address")
Reported-by: Liam Merwick <liam.merwick@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Message-Id: <20220120010719.711476-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2022-01-20 01:07:12 +00:00 committed by Greg Kroah-Hartman
parent abae88fb37
commit a2c8e1d9e4
2 changed files with 0 additions and 8 deletions
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7
arch/x86/kvm/svm/svm.c
View file

@ -4146,13 +4146,6 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i
if (likely(!insn || insn_len))
return true;
/*
* If RIP is invalid, go ahead with emulation which will cause an
* internal error exit.
*/
if (!kvm_vcpu_gfn_to_memslot(vcpu, kvm_rip_read(vcpu) >> PAGE_SHIFT))
return true;
cr4 = kvm_read_cr4(vcpu);
smep = cr4 & X86_CR4_SMEP;
smap = cr4 & X86_CR4_SMAP;

1
virt/kvm/kvm_main.c
View file

@ -1691,7 +1691,6 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn
{
return __gfn_to_memslot(kvm_vcpu_memslots(vcpu), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot);
bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{