Messages in this thread | | | Subject | Re: [PATCH v2 3/3] kvm: svm: Use the hardware provided GPA instead of page walk | From | Brijesh Singh <> | Date | Thu, 8 Dec 2016 09:39:59 -0600 |
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Hi Paolo,
On 12/08/2016 08:52 AM, Paolo Bonzini wrote: > > > On 23/11/2016 18:02, Brijesh Singh wrote: >> From: Tom Lendacky <thomas.lendacky@amd.com> >> >> When a guest causes a NPF which requires emulation, KVM sometimes walks >> the guest page tables to translate the GVA to a GPA. This is unnecessary >> most of the time on AMD hardware since the hardware provides the GPA in >> EXITINFO2. >> >> The only exception cases involve string operations involving rep or >> operations that use two memory locations. With rep, the GPA will only be >> the value of the initial NPF and with dual memory locations we won't know >> which memory address was translated into EXITINFO2. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> >> Reviewed-by: Borislav Petkov <bp@suse.de> >> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > > Tom, Brijesh, > > I would like to confirm that you have run kvm-unit-tests with this patch? > I haven't yet tried AMD (will do before sending the pull request to Linus), > but a similar patch for Intel gives me these 4 failures on emulator.flat: > > FAIL: push mem > FAIL: pop mem > FAIL: cross-page mmio read > FAIL: cross-page mmio write >
I did not ran kvm-unit-tests. However, I was able to boot Linux guest and run some stress test. I will run kvm-unit-tests and let you know soon.
-Brijesh > The VMX patch to set gpa_available is just this: > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 25d48380c312..5d7b60d4795b 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -6393,6 +6393,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu) > /* ept page table is present? */ > error_code |= (exit_qualification & 0x38) != 0; > > + vcpu->arch.gpa_available = true; > vcpu->arch.exit_qualification = exit_qualification; > > return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0); > @@ -6410,6 +6411,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu) > } > > ret = handle_mmio_page_fault(vcpu, gpa, true); > + vcpu->arch.gpa_available = true; > if (likely(ret == RET_MMIO_PF_EMULATE)) > return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) == > EMULATE_DONE; > @@ -8524,6 +8526,7 @@ 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 > > Thanks, > > Paolo > >> --- >> arch/x86/include/asm/kvm_emulate.h | 3 +++ >> arch/x86/include/asm/kvm_host.h | 3 +++ >> arch/x86/kvm/svm.c | 2 ++ >> arch/x86/kvm/x86.c | 17 ++++++++++++++++- >> 4 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h >> index e9cd7be..2d1ac09 100644 >> --- a/arch/x86/include/asm/kvm_emulate.h >> +++ b/arch/x86/include/asm/kvm_emulate.h >> @@ -344,6 +344,9 @@ struct x86_emulate_ctxt { >> struct read_cache mem_read; >> }; >> >> +/* String operation identifier (matches the definition in emulate.c) */ >> +#define CTXT_STRING_OP (1 << 13) >> + >> /* Repeat String Operation Prefix */ >> #define REPE_PREFIX 0xf3 >> #define REPNE_PREFIX 0xf2 >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> index 77cb3f9..fd5b1c8 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -668,6 +668,9 @@ struct kvm_vcpu_arch { >> >> int pending_ioapic_eoi; >> int pending_external_vector; >> + >> + /* GPA available (AMD only) */ >> + bool gpa_available; >> }; >> >> struct kvm_lpage_info { >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index 5e64e656..1bbd04c 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -4246,6 +4246,8 @@ static int handle_exit(struct kvm_vcpu *vcpu) >> return 1; >> } >> >> + vcpu->arch.gpa_available = (exit_code == SVM_EXIT_NPF); >> + >> return svm_exit_handlers[exit_code](svm); >> } >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index c30f62dc..5002eea 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -4441,7 +4441,19 @@ static int vcpu_mmio_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva, >> return 1; >> } >> >> - *gpa = vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, access, exception); >> + /* >> + * If the exit was due to a NPF we may already have a GPA. >> + * If the GPA is present, use it to avoid the GVA to GPA table >> + * walk. Note, this cannot be used on string operations since >> + * string operation using rep will only have the initial GPA >> + * from when the NPF occurred. >> + */ >> + if (vcpu->arch.gpa_available && >> + !(vcpu->arch.emulate_ctxt.d & CTXT_STRING_OP)) >> + *gpa = exception->address; >> + else >> + *gpa = vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, access, >> + exception); >> >> if (*gpa == UNMAPPED_GVA) >> return -1; >> @@ -5563,6 +5575,9 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, >> } >> >> restart: >> + /* Save the faulting GPA (cr2) in the address field */ >> + ctxt->exception.address = cr2; >> + >> r = x86_emulate_insn(ctxt); >> >> if (r == EMULATION_INTERCEPTED) >> >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >>
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