[PATCH 0/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[PATCH 0/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Wanpeng Li]

This patchset introduces a Force Emulation Prefix (ud2a; .ascii "kvm") 
for "emulate the next instruction", the codes will be executed by emulator 
instead of processor, for testing purposes.

A testcase here:

#include <stdio.h>
#include <string.h>
   
#define HYPERVISOR_INFO 0x40000000
   
#define CPUID(idx, eax, ebx, ecx, edx)\
    asm volatile (\
    "ud2a; .ascii \"kvm\"; 1: cpuid" \
    :"=b" (*ebx), "=a" (*eax),"=c" (*ecx), "=d" (*edx)\
        :"0"(idx) );  
   
void main()  
{  
	unsigned int eax,ebx,ecx,edx;  
	char string[13];  
   
	CPUID(HYPERVISOR_INFO, &eax, &ebx, &ecx, &edx);  
	*(unsigned int *)(string+0) = ebx;  
	*(unsigned int *)(string+4) = ecx;  
	*(unsigned int *)(string+8) = edx;  
   
	string[12] = 0;  
	if (strncmp(string, "KVMKVMKVM\0\0\0",12) == 0)
		printf("kvm guest\n");  
	else  
		printf("bare hardware\n");  
}

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>

Wanpeng Li (2):
  KVM: VMX: Introduce handle_ud()
  KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

 arch/x86/kvm/vmx.c | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

-- 
2.7.4

[PATCH 1/2] KVM: VMX: Introduce handle_ud()

[Wanpeng Li]

From: Wanpeng Li <wanpengli@tencent.com>

Introduce handle_ud() to handle invalid opcode, this function will be 
used by later patches.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 arch/x86/kvm/vmx.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9bc05f5..0f99833 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6215,6 +6215,18 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int handle_ud(struct kvm_vcpu *vcpu)
+{
+	enum emulation_result er;
+
+	er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
+	if (er == EMULATE_USER_EXIT)
+		return 0;
+	if (er != EMULATE_DONE)
+		kvm_queue_exception(vcpu, UD_VECTOR);
+	return 1;
+}
+
 static int handle_exception(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -6233,14 +6245,8 @@ static int handle_exception(struct kvm_vcpu *vcpu)
 	if (is_nmi(intr_info))
 		return 1;  /* already handled by vmx_vcpu_run() */
 
-	if (is_invalid_opcode(intr_info)) {
-		er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
-		if (er == EMULATE_USER_EXIT)
-			return 0;
-		if (er != EMULATE_DONE)
-			kvm_queue_exception(vcpu, UD_VECTOR);
-		return 1;
-	}
+	if (is_invalid_opcode(intr_info))
+		return handle_ud(vcpu);
 
 	error_code = 0;
 	if (intr_info & INTR_INFO_DELIVER_CODE_MASK)
-- 
2.7.4

[PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Wanpeng Li]

From: Wanpeng Li <wanpengli@tencent.com>

This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for 
"emulate the next instruction", the codes will be executed by emulator 
instead of processor, for testing purposes.

A testcase here:

#include <stdio.h>
#include <string.h>
   
#define HYPERVISOR_INFO 0x40000000
   
#define CPUID(idx, eax, ebx, ecx, edx)\
    asm volatile (\
    "ud2a; .ascii \"kvm\"; 1: cpuid" \
    :"=b" (*ebx), "=a" (*eax),"=c" (*ecx), "=d" (*edx)\
        :"0"(idx) );  
   
void main()  
{  
	unsigned int eax,ebx,ecx,edx;  
	char string[13];  
   
	CPUID(HYPERVISOR_INFO, &eax, &ebx, &ecx, &edx);  
	*(unsigned int *)(string+0) = ebx;  
	*(unsigned int *)(string+4) = ecx;  
	*(unsigned int *)(string+8) = edx;  
   
	string[12] = 0;  
	if (strncmp(string, "KVMKVMKVM\0\0\0",12) == 0)
		printf("kvm guest\n");  
	else  
		printf("bare hardware\n");  
}

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 arch/x86/kvm/vmx.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0f99833..90abed8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -108,6 +108,9 @@ module_param_named(enable_shadow_vmcs, enable_shadow_vmcs, bool, S_IRUGO);
 static bool __read_mostly nested = 0;
 module_param(nested, bool, S_IRUGO);
 
+static bool __read_mostly fep = 0;
+module_param(fep, bool, S_IRUGO);
+
 static u64 __read_mostly host_xss;
 
 static bool __read_mostly enable_pml = 1;
@@ -6218,8 +6221,21 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
 static int handle_ud(struct kvm_vcpu *vcpu)
 {
 	enum emulation_result er;
+	int emulation_type = EMULTYPE_TRAP_UD;
+
+	if (fep) {
+		char sig[5]; /* ud2; .ascii "kvm" */
+		struct x86_exception e;
+
+		kvm_read_guest_virt(&vcpu->arch.emulate_ctxt,
+				kvm_get_linear_rip(vcpu), sig, sizeof(sig), &e);
+		if (memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) {
+			emulation_type = 0;
+			kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));
+		}
+	}
 
-	er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
+	er = emulate_instruction(vcpu, emulation_type);
 	if (er == EMULATE_USER_EXIT)
 		return 0;
 	if (er != EMULATE_DONE)
-- 
2.7.4

Re: [PATCH 1/2] KVM: VMX: Introduce handle_ud()

[Konrad Rzeszutek Wilk]

On Mon, Mar 26, 2018 at 07:12:14PM -0700, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> Introduce handle_ud() to handle invalid opcode, this function will be 
> used by later patches.
> 
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Thank you!
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  arch/x86/kvm/vmx.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 9bc05f5..0f99833 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6215,6 +6215,18 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
>  	return 1;
>  }
>  
> +static int handle_ud(struct kvm_vcpu *vcpu)
> +{
> +	enum emulation_result er;
> +
> +	er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
> +	if (er == EMULATE_USER_EXIT)
> +		return 0;
> +	if (er != EMULATE_DONE)
> +		kvm_queue_exception(vcpu, UD_VECTOR);
> +	return 1;
> +}
> +
>  static int handle_exception(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> @@ -6233,14 +6245,8 @@ static int handle_exception(struct kvm_vcpu *vcpu)
>  	if (is_nmi(intr_info))
>  		return 1;  /* already handled by vmx_vcpu_run() */
>  
> -	if (is_invalid_opcode(intr_info)) {
> -		er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
> -		if (er == EMULATE_USER_EXIT)
> -			return 0;
> -		if (er != EMULATE_DONE)
> -			kvm_queue_exception(vcpu, UD_VECTOR);
> -		return 1;
> -	}
> +	if (is_invalid_opcode(intr_info))
> +		return handle_ud(vcpu);
>  
>  	error_code = 0;
>  	if (intr_info & INTR_INFO_DELIVER_CODE_MASK)
> -- 
> 2.7.4
> 

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Konrad Rzeszutek Wilk]

On Mon, Mar 26, 2018 at 07:12:15PM -0700, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for 
> "emulate the next instruction", the codes will be executed by emulator 
> instead of processor, for testing purposes.

Can you expand a bit ? Why do you want this in KVM in the first place?
Should this be controlled by a boolean parameter? 
> 
> A testcase here:
> 
> #include <stdio.h>
> #include <string.h>
>    
> #define HYPERVISOR_INFO 0x40000000
>    
> #define CPUID(idx, eax, ebx, ecx, edx)\
>     asm volatile (\
>     "ud2a; .ascii \"kvm\"; 1: cpuid" \
>     :"=b" (*ebx), "=a" (*eax),"=c" (*ecx), "=d" (*edx)\
>         :"0"(idx) );  
>    
> void main()  
> {  
> 	unsigned int eax,ebx,ecx,edx;  
> 	char string[13];  
>    
> 	CPUID(HYPERVISOR_INFO, &eax, &ebx, &ecx, &edx);  
> 	*(unsigned int *)(string+0) = ebx;  
> 	*(unsigned int *)(string+4) = ecx;  
> 	*(unsigned int *)(string+8) = edx;  
>    
> 	string[12] = 0;  
> 	if (strncmp(string, "KVMKVMKVM\0\0\0",12) == 0)
> 		printf("kvm guest\n");  
> 	else  
> 		printf("bare hardware\n");  
> }
> 
> Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  arch/x86/kvm/vmx.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 0f99833..90abed8 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -108,6 +108,9 @@ module_param_named(enable_shadow_vmcs, enable_shadow_vmcs, bool, S_IRUGO);
>  static bool __read_mostly nested = 0;
>  module_param(nested, bool, S_IRUGO);
>  
> +static bool __read_mostly fep = 0;
> +module_param(fep, bool, S_IRUGO);
> +
>  static u64 __read_mostly host_xss;
>  
>  static bool __read_mostly enable_pml = 1;
> @@ -6218,8 +6221,21 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
>  static int handle_ud(struct kvm_vcpu *vcpu)
>  {
>  	enum emulation_result er;
> +	int emulation_type = EMULTYPE_TRAP_UD;
> +
> +	if (fep) {
> +		char sig[5]; /* ud2; .ascii "kvm" */
> +		struct x86_exception e;

Don't you want to do = { };
to memset it?
> +
> +		kvm_read_guest_virt(&vcpu->arch.emulate_ctxt,
> +				kvm_get_linear_rip(vcpu), sig, sizeof(sig), &e);
> +		if (memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) {
> +			emulation_type = 0;
> +			kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));
> +		}
> +	}
>  
> -	er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
> +	er = emulate_instruction(vcpu, emulation_type);
>  	if (er == EMULATE_USER_EXIT)
>  		return 0;
>  	if (er != EMULATE_DONE)
> -- 
> 2.7.4
> 

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Konrad Rzeszutek Wilk]

On Tue, Mar 27, 2018 at 12:40:20AM -0400, Konrad Rzeszutek Wilk wrote:
> On Mon, Mar 26, 2018 at 07:12:15PM -0700, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@tencent.com>
> > 
> > This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for 
> > "emulate the next instruction", the codes will be executed by emulator 
> > instead of processor, for testing purposes.
> 
> Can you expand a bit ? Why do you want this in KVM in the first place?
> Should this be controlled by a boolean parameter? 

.. per guest. That is instead of a global one, have a per guest one?

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Wanpeng Li]

2018-03-27 12:55 GMT+08:00 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>:
> On Tue, Mar 27, 2018 at 12:40:20AM -0400, Konrad Rzeszutek Wilk wrote:
>> On Mon, Mar 26, 2018 at 07:12:15PM -0700, Wanpeng Li wrote:
>> > From: Wanpeng Li <wanpengli@tencent.com>
>> >
>> > This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for
>> > "emulate the next instruction", the codes will be executed by emulator
>> > instead of processor, for testing purposes.
>>
>> Can you expand a bit ? Why do you want this in KVM in the first place?

Please refer to the original discussion(Force Emulation Prefix part).
https://lkml.org/lkml/2018/3/22/220

>> Should this be controlled by a boolean parameter?
>
> .. per guest. That is instead of a global one, have a per guest one?

As Paolo pointed out offline:
> Testing without the hacks being done by emulator.flat (TLB mismatch between instructions and data).
I think a global module is enough for testing.

Regards,
Wanpeng Li

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Wanpeng Li]

2018-03-27 12:40 GMT+08:00 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>:
> On Mon, Mar 26, 2018 at 07:12:15PM -0700, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpengli@tencent.com>
>>
>> This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for
>> "emulate the next instruction", the codes will be executed by emulator
>> instead of processor, for testing purposes.
>
> Can you expand a bit ? Why do you want this in KVM in the first place?
> Should this be controlled by a boolean parameter?
>>
>> A testcase here:
>>
>> #include <stdio.h>
>> #include <string.h>
>>
>> #define HYPERVISOR_INFO 0x40000000
>>
>> #define CPUID(idx, eax, ebx, ecx, edx)\
>>     asm volatile (\
>>     "ud2a; .ascii \"kvm\"; 1: cpuid" \
>>     :"=b" (*ebx), "=a" (*eax),"=c" (*ecx), "=d" (*edx)\
>>         :"0"(idx) );
>>
>> void main()
>> {
>>       unsigned int eax,ebx,ecx,edx;
>>       char string[13];
>>
>>       CPUID(HYPERVISOR_INFO, &eax, &ebx, &ecx, &edx);
>>       *(unsigned int *)(string+0) = ebx;
>>       *(unsigned int *)(string+4) = ecx;
>>       *(unsigned int *)(string+8) = edx;
>>
>>       string[12] = 0;
>>       if (strncmp(string, "KVMKVMKVM\0\0\0",12) == 0)
>>               printf("kvm guest\n");
>>       else
>>               printf("bare hardware\n");
>> }
>>
>> Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
>> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
>> ---
>>  arch/x86/kvm/vmx.c | 18 +++++++++++++++++-
>>  1 file changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 0f99833..90abed8 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -108,6 +108,9 @@ module_param_named(enable_shadow_vmcs, enable_shadow_vmcs, bool, S_IRUGO);
>>  static bool __read_mostly nested = 0;
>>  module_param(nested, bool, S_IRUGO);
>>
>> +static bool __read_mostly fep = 0;
>> +module_param(fep, bool, S_IRUGO);
>> +
>>  static u64 __read_mostly host_xss;
>>
>>  static bool __read_mostly enable_pml = 1;
>> @@ -6218,8 +6221,21 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
>>  static int handle_ud(struct kvm_vcpu *vcpu)
>>  {
>>       enum emulation_result er;
>> +     int emulation_type = EMULTYPE_TRAP_UD;
>> +
>> +     if (fep) {
>> +             char sig[5]; /* ud2; .ascii "kvm" */
>> +             struct x86_exception e;
>
> Don't you want to do = { };
> to memset it?

sig buffer will be filled by insns which are fetched from guest
memory, so I think not memset is fine.

Regards,
Wanpeng Li

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Konrad Rzeszutek Wilk]

On Tue, Mar 27, 2018 at 01:03:15PM +0800, Wanpeng Li wrote:
> 2018-03-27 12:55 GMT+08:00 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>:
> > On Tue, Mar 27, 2018 at 12:40:20AM -0400, Konrad Rzeszutek Wilk wrote:
> >> On Mon, Mar 26, 2018 at 07:12:15PM -0700, Wanpeng Li wrote:
> >> > From: Wanpeng Li <wanpengli@tencent.com>
> >> >
> >> > This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for
> >> > "emulate the next instruction", the codes will be executed by emulator
> >> > instead of processor, for testing purposes.
> >>
> >> Can you expand a bit ? Why do you want this in KVM in the first place?
> 
> Please refer to the original discussion(Force Emulation Prefix part).
> https://lkml.org/lkml/2018/3/22/220

That really should be part massaged in this patch as part of the description.
> 
> >> Should this be controlled by a boolean parameter?
> >
> > .. per guest. That is instead of a global one, have a per guest one?
> 
> As Paolo pointed out offline:
> > Testing without the hacks being done by emulator.flat (TLB mismatch between instructions and data).

And also this above.

> I think a global module is enough for testing.

If so, perhaps have it wrapped with #ifdef DEBUG?

No need to put code gadgets that won't be utilized 99% of time.

> 
> Regards,
> Wanpeng Li

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Paolo Bonzini]

On 27/03/2018 07:18, Konrad Rzeszutek Wilk wrote:
>> I think a global module is enough for testing.
> If so, perhaps have it wrapped with #ifdef DEBUG?
> 
> No need to put code gadgets that won't be utilized 99% of time.

It is going to be used a lot in testing, actually.  There are quite a
few emulate.c bugfixes that are hard to test (see for example the
syscall eflags.tf bug that can currently be tested only on Intel) and
having something like this can only improve our coverage.

#ifdef DEBUG is almost always a bad idea, and though I agree that the
commit messages can be improved, I think the module parameter is the way
to go.

Wanpeng, can you also add it to svm.c?

Thanks,

Paolo

Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction"

[Wanpeng Li]

2018-03-27 15:25 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> On 27/03/2018 07:18, Konrad Rzeszutek Wilk wrote:
>>> I think a global module is enough for testing.
>> If so, perhaps have it wrapped with #ifdef DEBUG?
>>
>> No need to put code gadgets that won't be utilized 99% of time.
>
> It is going to be used a lot in testing, actually.  There are quite a
> few emulate.c bugfixes that are hard to test (see for example the
> syscall eflags.tf bug that can currently be tested only on Intel) and
> having something like this can only improve our coverage.
>
> #ifdef DEBUG is almost always a bad idea, and though I agree that the
> commit messages can be improved, I think the module parameter is the way
> to go.
>
> Wanpeng, can you also add it to svm.c?

Yeah, thanks for the review. :)

Regards,
Wanpeng Li

Re: [PATCH 1/2] KVM: VMX: Introduce handle_ud()

[Liran Alon]

----- kernellwp@gmail.com wrote:

> From: Wanpeng Li <wanpengli@tencent.com>
> 
> Introduce handle_ud() to handle invalid opcode, this function will be
> 
> used by later patches.
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  arch/x86/kvm/vmx.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 9bc05f5..0f99833 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6215,6 +6215,18 @@ static int handle_machine_check(struct kvm_vcpu
> *vcpu)
>  	return 1;
>  }
>  
> +static int handle_ud(struct kvm_vcpu *vcpu)
> +{
> +	enum emulation_result er;
> +
> +	er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
> +	if (er == EMULATE_USER_EXIT)
> +		return 0;
> +	if (er != EMULATE_DONE)
> +		kvm_queue_exception(vcpu, UD_VECTOR);
> +	return 1;
> +}
> +
>  static int handle_exception(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> @@ -6233,14 +6245,8 @@ static int handle_exception(struct kvm_vcpu
> *vcpu)
>  	if (is_nmi(intr_info))
>  		return 1;  /* already handled by vmx_vcpu_run() */
>  
> -	if (is_invalid_opcode(intr_info)) {
> -		er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
> -		if (er == EMULATE_USER_EXIT)
> -			return 0;
> -		if (er != EMULATE_DONE)
> -			kvm_queue_exception(vcpu, UD_VECTOR);
> -		return 1;
> -	}
> +	if (is_invalid_opcode(intr_info))
> +		return handle_ud(vcpu);
>  
>  	error_code = 0;
>  	if (intr_info & INTR_INFO_DELIVER_CODE_MASK)
> -- 
> 2.7.4

Reviewed-By: Liran Alon <liran.alon@oracle.com>