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[PATCH v2 1/5] KVM: x86: Add a return value to kvm_emulate_cpuid

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Once skipping the emulated instruction can potentially trigger an exit to
userspace (via KVM_GUESTDBG_SINGLESTEP) kvm_emulate_cpuid will need to
propagate a return value.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
 arch/x86/include/asm/kvm_host.h | 2 +-
 arch/x86/kvm/cpuid.c            | 3 ++-
 arch/x86/kvm/svm.c              | 3 +--
 arch/x86/kvm/vmx.c              | 3 +--
 4 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 77cb3f9..80bad5c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1129,17 +1129,17 @@ void kvm_enable_efer_bits(u64);
 bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer);
 int kvm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr);
 int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr);
 
 struct x86_emulate_ctxt;
 
 int kvm_fast_pio_out(struct kvm_vcpu *vcpu, int size, unsigned short port);
 int kvm_fast_pio_in(struct kvm_vcpu *vcpu, int size, unsigned short port);
-void kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
+int kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
 int kvm_emulate_halt(struct kvm_vcpu *vcpu);
 int kvm_vcpu_halt(struct kvm_vcpu *vcpu);
 int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);
 
 void kvm_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
 int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int seg);
 void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
 
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 25f0f15..07cc629 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -874,22 +874,23 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
 		*ecx = best->ecx;
 		*edx = best->edx;
 	} else
 		*eax = *ebx = *ecx = *edx = 0;
 	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx);
 }
 EXPORT_SYMBOL_GPL(kvm_cpuid);
 
-void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
+int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
 {
 	u32 eax, ebx, ecx, edx;
 
 	eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
 	ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
 	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);
 	kvm_register_write(vcpu, VCPU_REGS_RAX, eax);
 	kvm_register_write(vcpu, VCPU_REGS_RBX, ebx);
 	kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);
 	kvm_register_write(vcpu, VCPU_REGS_RDX, edx);
 	kvm_x86_ops->skip_emulated_instruction(vcpu);
+	return 1;
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5e64e656..5bdffcd 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3234,18 +3234,17 @@ static int task_switch_interception(struct vcpu_svm *svm)
 		return 0;
 	}
 	return 1;
 }
 
 static int cpuid_interception(struct vcpu_svm *svm)
 {
 	svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
-	kvm_emulate_cpuid(&svm->vcpu);
-	return 1;
+	return kvm_emulate_cpuid(&svm->vcpu);
 }
 
 static int iret_interception(struct vcpu_svm *svm)
 {
 	++svm->vcpu.stat.nmi_window_exits;
 	clr_intercept(svm, INTERCEPT_IRET);
 	svm->vcpu.arch.hflags |= HF_IRET_MASK;
 	svm->nmi_iret_rip = kvm_rip_read(&svm->vcpu);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0e86219..e4af9699 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5832,18 +5832,17 @@ static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu)
 
 static void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val)
 {
 	vmcs_writel(GUEST_DR7, val);
 }
 
 static int handle_cpuid(struct kvm_vcpu *vcpu)
 {
-	kvm_emulate_cpuid(vcpu);
-	return 1;
+	return kvm_emulate_cpuid(vcpu);
 }
 
 static int handle_rdmsr(struct kvm_vcpu *vcpu)
 {
 	u32 ecx = vcpu->arch.regs[VCPU_REGS_RCX];
 	struct msr_data msr_info;
 
 	msr_info.index = ecx;
-- 
2.10.2

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Thread

[PATCH v2 0/5] KVM: VMX: Fix single stepping with emulated instructions Kyle Huey <me@kylehuey.com> - 2016-11-29 21:50 +0100
  [PATCH v2 1/5] KVM: x86: Add a return value to kvm_emulate_cpuid Kyle Huey <me@kylehuey.com> - 2016-11-29 21:50 +0100
  [PATCH v2 3/5] KVM: VMX: Move skip_emulated_instruction out of nested_vmx_check_vmcs12 Kyle Huey <me@kylehuey.com> - 2016-11-29 21:50 +0100
  [PATCH v2 2/5] KVM: VMX: Reorder some skip_emulated_instruction calls Kyle Huey <me@kylehuey.com> - 2016-11-29 21:50 +0100
  [PATCH v2 4/5] KVM: x86: Add kvm_skip_emulated_instruction and use it. Kyle Huey <me@kylehuey.com> - 2016-11-29 21:50 +0100
  Re: [PATCH v2 0/5] KVM: VMX: Fix single stepping with emulated  instructions Radim Krčmář <rkrcmar@redhat.com> - 2016-11-30 19:50 +0100
    Re: [PATCH v2 0/5] KVM: VMX: Fix single stepping with emulated instructions Kyle Huey <me@kylehuey.com> - 2016-11-30 20:00 +0100

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