diff mbox series

[v2,1/4] KVM: x86: Factor out x86 instruction emulation with decoding

Message ID 20210121065508.1169585-2-wei.huang2@amd.com (mailing list archive)
State New, archived
Headers show
Series Handle #GP for SVM execution instructions | expand

Commit Message

Wei Huang Jan. 21, 2021, 6:55 a.m. UTC 
Move the instruction decode part out of x86_emulate_instruction() for it
to be used in other places. Also kvm_clear_exception_queue() is moved
inside the if-statement as it doesn't apply when KVM are coming back from
userspace.

Co-developed-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
---
 arch/x86/kvm/x86.c | 63 +++++++++++++++++++++++++++++-----------------
 arch/x86/kvm/x86.h |  2 ++
 2 files changed, 42 insertions(+), 23 deletions(-)

Comments

Maxim Levitsky Jan. 21, 2021, 2:04 p.m. UTC | #1 
On Thu, 2021-01-21 at 01:55 -0500, Wei Huang wrote:
> Move the instruction decode part out of x86_emulate_instruction() for it
> to be used in other places. Also kvm_clear_exception_queue() is moved
> inside the if-statement as it doesn't apply when KVM are coming back from
> userspace.
> 
> Co-developed-by: Bandan Das <bsd@redhat.com>
> Signed-off-by: Bandan Das <bsd@redhat.com>
> Signed-off-by: Wei Huang <wei.huang2@amd.com>
> ---
>  arch/x86/kvm/x86.c | 63 +++++++++++++++++++++++++++++-----------------
>  arch/x86/kvm/x86.h |  2 ++
>  2 files changed, 42 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9a8969a6dd06..580883cee493 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7298,6 +7298,43 @@ static bool is_vmware_backdoor_opcode(struct x86_emulate_ctxt *ctxt)
>  	return false;
>  }
>  
> +/*
> + * Decode and emulate instruction. Return EMULATION_OK if success.
> + */
> +int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu, int emulation_type,
> +				    void *insn, int insn_len)

Isn't the name of this function wrong? This function decodes the instruction.
So I would expect something like x86_decode_instruction.

> +{
> +	int r = EMULATION_OK;
> +	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
> +
> +	init_emulate_ctxt(vcpu);
> +
> +	/*
> +	 * We will reenter on the same instruction since
> +	 * we do not set complete_userspace_io.  This does not
> +	 * handle watchpoints yet, those would be handled in
> +	 * the emulate_ops.
> +	 */
> +	if (!(emulation_type & EMULTYPE_SKIP) &&
> +	    kvm_vcpu_check_breakpoint(vcpu, &r))
> +		return r;
> +
> +	ctxt->interruptibility = 0;
> +	ctxt->have_exception = false;
> +	ctxt->exception.vector = -1;
> +	ctxt->perm_ok = false;
> +
> +	ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
> +
> +	r = x86_decode_insn(ctxt, insn, insn_len);
> +
> +	trace_kvm_emulate_insn_start(vcpu);
> +	++vcpu->stat.insn_emulation;
> +
> +	return r;
> +}
> +EXPORT_SYMBOL_GPL(x86_emulate_decoded_instruction);
> +
>  int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  			    int emulation_type, void *insn, int insn_len)
>  {
> @@ -7317,32 +7354,12 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  	 */
>  	write_fault_to_spt = vcpu->arch.write_fault_to_shadow_pgtable;
>  	vcpu->arch.write_fault_to_shadow_pgtable = false;
> -	kvm_clear_exception_queue(vcpu);

I think that this change is OK, but I can't be 100% sure about this.

Best regards,
	Maxim Levitsky


>  
>  	if (!(emulation_type & EMULTYPE_NO_DECODE)) {
> -		init_emulate_ctxt(vcpu);
> -
> -		/*
> -		 * We will reenter on the same instruction since
> -		 * we do not set complete_userspace_io.  This does not
> -		 * handle watchpoints yet, those would be handled in
> -		 * the emulate_ops.
> -		 */
> -		if (!(emulation_type & EMULTYPE_SKIP) &&
> -		    kvm_vcpu_check_breakpoint(vcpu, &r))
> -			return r;
> -
> -		ctxt->interruptibility = 0;
> -		ctxt->have_exception = false;
> -		ctxt->exception.vector = -1;
> -		ctxt->perm_ok = false;
> -
> -		ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
> -
> -		r = x86_decode_insn(ctxt, insn, insn_len);
> +		kvm_clear_exception_queue(vcpu);
>  
> -		trace_kvm_emulate_insn_start(vcpu);
> -		++vcpu->stat.insn_emulation;
> +		r = x86_emulate_decoded_instruction(vcpu, emulation_type,
> +						    insn, insn_len);
>  		if (r != EMULATION_OK)  {
>  			if ((emulation_type & EMULTYPE_TRAP_UD) ||
>  			    (emulation_type & EMULTYPE_TRAP_UD_FORCED)) {
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index c5ee0f5ce0f1..fc42454a4c27 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -273,6 +273,8 @@ bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
>  					  int page_num);
>  bool kvm_vector_hashing_enabled(void);
>  void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
> +int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu, int emulation_type,
> +				    void *insn, int insn_len);
>  int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  			    int emulation_type, void *insn, int insn_len);
>  fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
Paolo Bonzini Jan. 21, 2021, 2:23 p.m. UTC | #2 
On 21/01/21 15:04, Maxim Levitsky wrote:
>> +int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu, int emulation_type,
>> +				    void *insn, int insn_len)
> Isn't the name of this function wrong? This function decodes the instruction.
> So I would expect something like x86_decode_instruction.
> 

Yes, that or x86_decode_emulated_instruction.

Paolo
Wei Huang Jan. 21, 2021, 3:31 p.m. UTC | #3 
On 1/21/21 8:23 AM, Paolo Bonzini wrote:
> On 21/01/21 15:04, Maxim Levitsky wrote:
>>> +int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu, int
>>> emulation_type,
>>> +                    void *insn, int insn_len)
>> Isn't the name of this function wrong? This function decodes the
>> instruction.
>> So I would expect something like x86_decode_instruction.
>>
> 
> Yes, that or x86_decode_emulated_instruction.

I was debating about it while making the change. I will update it to new
name in v3.

> 
> Paolo
>
diff mbox series

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a8969a6dd06..580883cee493 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7298,6 +7298,43 @@  static bool is_vmware_backdoor_opcode(struct x86_emulate_ctxt *ctxt)
 	return false;
 }
 
+/*
+ * Decode and emulate instruction. Return EMULATION_OK if success.
+ */
+int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu, int emulation_type,
+				    void *insn, int insn_len)
+{
+	int r = EMULATION_OK;
+	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
+
+	init_emulate_ctxt(vcpu);
+
+	/*
+	 * We will reenter on the same instruction since
+	 * we do not set complete_userspace_io.  This does not
+	 * handle watchpoints yet, those would be handled in
+	 * the emulate_ops.
+	 */
+	if (!(emulation_type & EMULTYPE_SKIP) &&
+	    kvm_vcpu_check_breakpoint(vcpu, &r))
+		return r;
+
+	ctxt->interruptibility = 0;
+	ctxt->have_exception = false;
+	ctxt->exception.vector = -1;
+	ctxt->perm_ok = false;
+
+	ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
+
+	r = x86_decode_insn(ctxt, insn, insn_len);
+
+	trace_kvm_emulate_insn_start(vcpu);
+	++vcpu->stat.insn_emulation;
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(x86_emulate_decoded_instruction);
+
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len)
 {
@@ -7317,32 +7354,12 @@  int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	 */
 	write_fault_to_spt = vcpu->arch.write_fault_to_shadow_pgtable;
 	vcpu->arch.write_fault_to_shadow_pgtable = false;
-	kvm_clear_exception_queue(vcpu);
 
 	if (!(emulation_type & EMULTYPE_NO_DECODE)) {
-		init_emulate_ctxt(vcpu);
-
-		/*
-		 * We will reenter on the same instruction since
-		 * we do not set complete_userspace_io.  This does not
-		 * handle watchpoints yet, those would be handled in
-		 * the emulate_ops.
-		 */
-		if (!(emulation_type & EMULTYPE_SKIP) &&
-		    kvm_vcpu_check_breakpoint(vcpu, &r))
-			return r;
-
-		ctxt->interruptibility = 0;
-		ctxt->have_exception = false;
-		ctxt->exception.vector = -1;
-		ctxt->perm_ok = false;
-
-		ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
-
-		r = x86_decode_insn(ctxt, insn, insn_len);
+		kvm_clear_exception_queue(vcpu);
 
-		trace_kvm_emulate_insn_start(vcpu);
-		++vcpu->stat.insn_emulation;
+		r = x86_emulate_decoded_instruction(vcpu, emulation_type,
+						    insn, insn_len);
 		if (r != EMULATION_OK)  {
 			if ((emulation_type & EMULTYPE_TRAP_UD) ||
 			    (emulation_type & EMULTYPE_TRAP_UD_FORCED)) {
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index c5ee0f5ce0f1..fc42454a4c27 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -273,6 +273,8 @@  bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 					  int page_num);
 bool kvm_vector_hashing_enabled(void);
 void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
+int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu, int emulation_type,
+				    void *insn, int insn_len);
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len);
 fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);