4.18-stable review patch. If anyone has any objections, please let me know.
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From: Sean Christopherson sean.j.christopherson@intel.com
commit 472faffacd9032164f611f56329d0025ddca55b5 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/mmu.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
--- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4960,7 +4960,7 @@ static int make_mmu_pages_available(stru int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code, void *insn, int insn_len) { - int r, emulation_type = EMULTYPE_ALLOW_RETRY; + int r, emulation_type = 0; enum emulation_result er; bool direct = vcpu->arch.mmu.direct_map;
@@ -4973,10 +4973,8 @@ int kvm_mmu_page_fault(struct kvm_vcpu * r = RET_PF_INVALID; if (unlikely(error_code & PFERR_RSVD_MASK)) { r = handle_mmio_page_fault(vcpu, cr2, direct); - if (r == RET_PF_EMULATE) { - emulation_type = 0; + if (r == RET_PF_EMULATE) goto emulate; - } }
if (r == RET_PF_INVALID) { @@ -5003,8 +5001,16 @@ int kvm_mmu_page_fault(struct kvm_vcpu * 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: /* * On AMD platforms, under certain conditions insn_len may be zero on #NPF.