From 618232e2196a6db1ed66b5e1ec049e5c46480f49 Mon Sep 17 00:00:00 2001 From: Brijesh Singh Date: Thu, 17 Aug 2017 18:36:57 +0200 Subject: [PATCH] KVM: x86: Avoid guest page table walk when gpa_available is set MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When a guest causes a page fault which requires emulation, the vcpu->arch.gpa_available flag is set to indicate that cr2 contains a valid GPA. Currently, emulator_read_write_onepage() makes use of gpa_available flag to avoid a guest page walk for a known MMIO regions. Lets not limit the gpa_available optimization to just MMIO region. The patch extends the check to avoid page walk whenever gpa_available flag is set. Signed-off-by: Brijesh Singh [Fix EPT=0 according to Wanpeng Li's fix, plus ensure VMX also uses the new code. - Paolo] Signed-off-by: Paolo Bonzini Reviewed-by: David Hildenbrand [Moved "ret < 0" to the else brach, as per David's review. - Radim] Signed-off-by: Radim Krčmář --- arch/x86/include/asm/kvm_host.h | 3 ++- arch/x86/kvm/mmu.c | 6 ++++++ arch/x86/kvm/svm.c | 2 -- arch/x86/kvm/vmx.c | 4 ---- arch/x86/kvm/x86.c | 24 +++++++++--------------- 5 files changed, 17 insertions(+), 22 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 9e4862e0e978..6db0ed9cf59e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -685,8 +685,9 @@ struct kvm_vcpu_arch { int pending_ioapic_eoi; int pending_external_vector; - /* GPA available (AMD only) */ + /* GPA available */ bool gpa_available; + gpa_t gpa_val; /* be preempted when it's in kernel-mode(cpl=0) */ bool preempted_in_kernel; diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index f7598883920a..a2c592b14617 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4843,6 +4843,12 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code, enum emulation_result er; bool direct = vcpu->arch.mmu.direct_map || mmu_is_nested(vcpu); + /* With shadow page tables, fault_address contains a GVA or nGPA. */ + if (vcpu->arch.mmu.direct_map) { + vcpu->arch.gpa_available = true; + vcpu->arch.gpa_val = cr2; + } + if (unlikely(error_code & PFERR_RSVD_MASK)) { r = handle_mmio_page_fault(vcpu, cr2, direct); if (r == RET_MMIO_PF_EMULATE) { diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 1fa9ee5660f4..a603d0c14a5a 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4236,8 +4236,6 @@ static int handle_exit(struct kvm_vcpu *vcpu) trace_kvm_exit(exit_code, vcpu, KVM_ISA_SVM); - vcpu->arch.gpa_available = (exit_code == SVM_EXIT_NPF); - if (!is_cr_intercept(svm, INTERCEPT_CR0_WRITE)) vcpu->arch.cr0 = svm->vmcb->save.cr0; if (npt_enabled) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 45fb0ea78ee8..e2c8b33c35d1 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -6393,9 +6393,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu) error_code |= (exit_qualification & 0x100) != 0 ? PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK; - vcpu->arch.gpa_available = true; vcpu->arch.exit_qualification = exit_qualification; - return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0); } @@ -6410,7 +6408,6 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu) return kvm_skip_emulated_instruction(vcpu); } - vcpu->arch.gpa_available = true; ret = kvm_mmu_page_fault(vcpu, gpa, PFERR_RSVD_MASK, NULL, 0); if (ret >= 0) return ret; @@ -8644,7 +8641,6 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) u32 vectoring_info = vmx->idt_vectoring_info; trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX); - vcpu->arch.gpa_available = false; /* * Flush logged GPAs PML buffer, this will make dirty_bitmap more diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e10eda86bc7b..4e699238a113 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4657,25 +4657,18 @@ static int emulator_read_write_onepage(unsigned long addr, void *val, */ if (vcpu->arch.gpa_available && emulator_can_use_gpa(ctxt) && - vcpu_is_mmio_gpa(vcpu, addr, exception->address, write) && - (addr & ~PAGE_MASK) == (exception->address & ~PAGE_MASK)) { - gpa = exception->address; - goto mmio; + (addr & ~PAGE_MASK) == (vcpu->arch.gpa_val & ~PAGE_MASK)) { + gpa = vcpu->arch.gpa_val; + ret = vcpu_is_mmio_gpa(vcpu, addr, gpa, write); + } else { + ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write); + if (ret < 0) + return X86EMUL_PROPAGATE_FAULT; } - ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write); - - if (ret < 0) - return X86EMUL_PROPAGATE_FAULT; - - /* For APIC access vmexit */ - if (ret) - goto mmio; - - if (ops->read_write_emulate(vcpu, gpa, val, bytes)) + if (!ret && ops->read_write_emulate(vcpu, gpa, val, bytes)) return X86EMUL_CONTINUE; -mmio: /* * Is this MMIO handled locally? */ @@ -7002,6 +6995,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) if (vcpu->arch.apic_attention) kvm_lapic_sync_from_vapic(vcpu); + vcpu->arch.gpa_available = false; r = kvm_x86_ops->handle_exit(vcpu); return r;