Commit c4762fda authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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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.

Hardcoded RIP advancement remains in vmrun_interception(), this is going to
be taken care of separately.

Reported-by: default avatarJim Mattson <jmattson@google.com>
Reviewed-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 02d4160f

arch/x86/kvm/svm.c

+0 −11
Original line number Diff line number Diff line
@@ -2900,13 +2900,11 @@ 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);

}
@@ -3694,7 +3692,6 @@ 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);
@@ -3721,7 +3718,6 @@ 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);
@@ -3772,7 +3768,6 @@ 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);
@@ -3788,7 +3783,6 @@ 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);
@@ -3813,7 +3807,6 @@ 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);

}
@@ -3836,7 +3829,6 @@ 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);

	}
@@ -3918,7 +3910,6 @@ fail: 


static int cpuid_interception(struct vcpu_svm *svm)

{

	svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;

	return kvm_emulate_cpuid(&svm->vcpu);

}
@@ -4248,7 +4239,6 @@ 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);

	}

}
@@ -4454,7 +4444,6 @@ 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);

	}

}

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