| Message ID | 147190824754.9523.13923968456167130181.stgit@brijesh-build-machine (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Aug 22, 2016 at 07:24:07PM -0400, 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> > --- > 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(-) FWIW, LGTM. (Gotta love replying in acronyms :-)) Reviewed-by: Borislav Petkov <bp@suse.de>
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 c38f878..b1dd673 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -667,6 +667,9 @@ 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 fd5a9a8..9b2de7c 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4055,6 +4055,8 @@ 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/x86.c b/arch/x86/kvm/x86.c index 78295b0..d6f2f4b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4382,7 +4382,19 @@ 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; @@ -5504,6 +5516,9 @@ 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)