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Date: Thu, 20 Jun 2019 13:02:40 +0200 From: Vitaly Kuznetsov <vkuznets@...hat.com> To: kvm@...r.kernel.org Cc: linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, Joerg Roedel <joro@...tes.org>, Jim Mattson <jmattson@...gle.com> Subject: [PATCH RFC 5/5] x86: KVM: svm: remove hardcoded instruction length from intercepts Various intercepts hard-code the respective instruction lengths to optimize skip_emulated_instruction(): when next_rip is pre-set we skip kvm_emulate_instruction(vcpu, EMULTYPE_SKIP). The optimization is, however, incorrect: different (redundant) prefixes could be used to enlarge the instruction. We can't really avoid decoding. svm->next_rip is not used when CPU supports 'nrips' (X86_FEATURE_NRIPS) feature: next RIP is provided in VMCB. The feature is not really new (Opteron G3s had it already) and the change should have zero affect. Remove manual svm->next_rip setting with hard-coded instruction lengths. The only case where we now use svm->next_rip is EXIT_IOIO: the instruction length is provided to us by hardware. Reported-by: Jim Mattson <jmattson@...gle.com> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com> --- arch/x86/kvm/svm.c | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 39e61029f401..4c29859fecde 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2890,13 +2890,11 @@ static int nop_on_interception(struct vcpu_svm *svm) static int halt_interception(struct vcpu_svm *svm) { - svm->next_rip = kvm_rip_read(&svm->vcpu) + 1; return kvm_emulate_halt(&svm->vcpu); } static int vmmcall_interception(struct vcpu_svm *svm) { - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; return kvm_emulate_hypercall(&svm->vcpu); } @@ -3684,7 +3682,6 @@ static int vmload_interception(struct vcpu_svm *svm) nested_vmcb = map.hva; - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; ret = kvm_skip_emulated_instruction(&svm->vcpu); nested_svm_vmloadsave(nested_vmcb, svm->vmcb); @@ -3711,7 +3708,6 @@ static int vmsave_interception(struct vcpu_svm *svm) nested_vmcb = map.hva; - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; ret = kvm_skip_emulated_instruction(&svm->vcpu); nested_svm_vmloadsave(svm->vmcb, nested_vmcb); @@ -3762,7 +3758,6 @@ static int stgi_interception(struct vcpu_svm *svm) if (vgif_enabled(svm)) clr_intercept(svm, INTERCEPT_STGI); - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; ret = kvm_skip_emulated_instruction(&svm->vcpu); kvm_make_request(KVM_REQ_EVENT, &svm->vcpu); @@ -3778,7 +3773,6 @@ static int clgi_interception(struct vcpu_svm *svm) if (nested_svm_check_permissions(svm)) return 1; - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; ret = kvm_skip_emulated_instruction(&svm->vcpu); disable_gif(svm); @@ -3803,7 +3797,6 @@ static int invlpga_interception(struct vcpu_svm *svm) /* Let's treat INVLPGA the same as INVLPG (can be optimized!) */ kvm_mmu_invlpg(vcpu, kvm_rax_read(&svm->vcpu)); - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; return kvm_skip_emulated_instruction(&svm->vcpu); } @@ -3826,7 +3819,6 @@ static int xsetbv_interception(struct vcpu_svm *svm) u32 index = kvm_rcx_read(&svm->vcpu); if (kvm_set_xcr(&svm->vcpu, index, new_bv) == 0) { - svm->next_rip = kvm_rip_read(&svm->vcpu) + 3; return kvm_skip_emulated_instruction(&svm->vcpu); } @@ -3903,7 +3895,6 @@ static int task_switch_interception(struct vcpu_svm *svm) static int cpuid_interception(struct vcpu_svm *svm) { - svm->next_rip = kvm_rip_read(&svm->vcpu) + 2; return kvm_emulate_cpuid(&svm->vcpu); } @@ -4233,7 +4224,6 @@ static int rdmsr_interception(struct vcpu_svm *svm) kvm_rax_write(&svm->vcpu, msr_info.data & 0xffffffff); kvm_rdx_write(&svm->vcpu, msr_info.data >> 32); - svm->next_rip = kvm_rip_read(&svm->vcpu) + 2; return kvm_skip_emulated_instruction(&svm->vcpu); } } @@ -4439,7 +4429,6 @@ static int wrmsr_interception(struct vcpu_svm *svm) return 1; } else { trace_kvm_msr_write(ecx, data); - svm->next_rip = kvm_rip_read(&svm->vcpu) + 2; return kvm_skip_emulated_instruction(&svm->vcpu); } } -- 2.20.1
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