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KVM: x86: Default to not allowing emulation retry in kvm_mmu_page_fault

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Effectively force kvm_mmu_page_fault() to opt-in to allowing retry to
make it more obvious when and why it allows emulation to be retried.
Previously this approach was less convenient due to retry and
re-execute behavior being controlled by separate flags that were also
inverted in their implementations (opt-in versus opt-out).

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Sean Christopherson 2018-08-23 13:56:50 -07:00 committed by Radim Krčmář
parent 384bf2218e
commit 472faffacd
1 changed files with 12 additions and 6 deletions
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18
arch/x86/kvm/mmu.c
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@ -5217,7 +5217,7 @@ static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code, int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
void *insn, int insn_len) void *insn, int insn_len)
{ {
int r, emulation_type = EMULTYPE_ALLOW_RETRY; int r, emulation_type = 0;
enum emulation_result er; enum emulation_result er;
bool direct = vcpu->arch.mmu.direct_map; bool direct = vcpu->arch.mmu.direct_map;
@ -5230,10 +5230,8 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
r = RET_PF_INVALID; r = RET_PF_INVALID;
if (unlikely(error_code & PFERR_RSVD_MASK)) { if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, cr2, direct); r = handle_mmio_page_fault(vcpu, cr2, direct);
if (r == RET_PF_EMULATE) { if (r == RET_PF_EMULATE)
emulation_type = 0;
goto emulate; goto emulate;
}
} }
if (r == RET_PF_INVALID) { if (r == RET_PF_INVALID) {
@ -5260,8 +5258,16 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
return 1; return 1;
} }
if (mmio_info_in_cache(vcpu, cr2, direct)) /*
emulation_type = 0; * vcpu->arch.mmu.page_fault returned RET_PF_EMULATE, but we can still
* optimistically try to just unprotect the page and let the processor
* re-execute the instruction that caused the page fault. Do not allow
* retrying MMIO emulation, as it's not only pointless but could also
* cause us to enter an infinite loop because the processor will keep
* faulting on the non-existent MMIO address.
*/
if (!mmio_info_in_cache(vcpu, cr2, direct))
emulation_type = EMULTYPE_ALLOW_RETRY;
emulate: emulate:
/* /*
* On AMD platforms, under certain conditions insn_len may be zero on #NPF. * On AMD platforms, under certain conditions insn_len may be zero on #NPF.