Instead of returning an opcode from svm_instr_opcode() and then passing
it to emulate_svm_instr(), which uses it to find the corresponding exit
code and intercept handler, return the exit code directly from
svm_instr_opcode(), and rename it to svm_instr_exit_code().
emulate_svm_instr() boils down to synthesizing a #VMEXIT or calling the
intercept handler, so open-code it in gp_interception(), and use
svm_invoke_exit_handler() to call the intercept handler based on
the exit code. This allows for dropping the SVM_INSTR_* enum, and the
const array mapping its values to exit codes and intercept handlers.
In gp_intercept(), handle SVM instructions first with an early return,
un-indenting the rest of the code.
No functional change intended.
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
---
arch/x86/kvm/svm/svm.c | 78 +++++++++++++++---------------------------
1 file changed, 27 insertions(+), 51 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index d2ca226871c2f..392a5088f20bf 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2233,54 +2233,26 @@ static int vmrun_interception(struct kvm_vcpu *vcpu)
return nested_svm_vmrun(vcpu);
}
-enum {
- NONE_SVM_INSTR,
- SVM_INSTR_VMRUN,
- SVM_INSTR_VMLOAD,
- SVM_INSTR_VMSAVE,
-};
-
-/* Return NONE_SVM_INSTR if not SVM instrs, otherwise return decode result */
-static int svm_instr_opcode(struct kvm_vcpu *vcpu)
+/* Return 0 if not SVM instr, otherwise return associated exit_code */
+static u64 svm_instr_exit_code(struct kvm_vcpu *vcpu)
{
struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
if (ctxt->b != 0x1 || ctxt->opcode_len != 2)
- return NONE_SVM_INSTR;
+ return 0;
switch (ctxt->modrm) {
case 0xd8: /* VMRUN */
- return SVM_INSTR_VMRUN;
+ return SVM_EXIT_VMRUN;
case 0xda: /* VMLOAD */
- return SVM_INSTR_VMLOAD;
+ return SVM_EXIT_VMLOAD;
case 0xdb: /* VMSAVE */
- return SVM_INSTR_VMSAVE;
+ return SVM_EXIT_VMSAVE;
default:
break;
}
- return NONE_SVM_INSTR;
-}
-
-static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
-{
- const int guest_mode_exit_codes[] = {
- [SVM_INSTR_VMRUN] = SVM_EXIT_VMRUN,
- [SVM_INSTR_VMLOAD] = SVM_EXIT_VMLOAD,
- [SVM_INSTR_VMSAVE] = SVM_EXIT_VMSAVE,
- };
- int (*const svm_instr_handlers[])(struct kvm_vcpu *vcpu) = {
- [SVM_INSTR_VMRUN] = vmrun_interception,
- [SVM_INSTR_VMLOAD] = vmload_interception,
- [SVM_INSTR_VMSAVE] = vmsave_interception,
- };
- struct vcpu_svm *svm = to_svm(vcpu);
-
- if (is_guest_mode(vcpu)) {
- nested_svm_simple_vmexit(svm, guest_mode_exit_codes[opcode]);
- return 1;
- }
- return svm_instr_handlers[opcode](vcpu);
+ return 0;
}
/*
@@ -2295,7 +2267,7 @@ static int gp_interception(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
u32 error_code = svm->vmcb->control.exit_info_1;
- int opcode;
+ u64 svm_exit_code;
/* Both #GP cases have zero error_code */
if (error_code)
@@ -2305,27 +2277,31 @@ static int gp_interception(struct kvm_vcpu *vcpu)
if (x86_decode_emulated_instruction(vcpu, 0, NULL, 0) != EMULATION_OK)
goto reinject;
- opcode = svm_instr_opcode(vcpu);
-
- if (opcode == NONE_SVM_INSTR) {
- if (!enable_vmware_backdoor)
- goto reinject;
-
- /*
- * VMware backdoor emulation on #GP interception only handles
- * IN{S}, OUT{S}, and RDPMC.
- */
- if (!is_guest_mode(vcpu))
- return kvm_emulate_instruction(vcpu,
- EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
- } else {
+ svm_exit_code = svm_instr_exit_code(vcpu);
+ if (svm_exit_code) {
/* All SVM instructions expect page aligned RAX */
if (svm->vmcb->save.rax & ~PAGE_MASK)
goto reinject;
- return emulate_svm_instr(vcpu, opcode);
+ if (is_guest_mode(vcpu)) {
+ nested_svm_simple_vmexit(svm, svm_exit_code);
+ return 1;
+ }
+
+ return svm_invoke_exit_handler(vcpu, svm_exit_code);
}
+ if (!enable_vmware_backdoor)
+ goto reinject;
+
+ /*
+ * VMware backdoor emulation on #GP interception only handles
+ * IN{S}, OUT{S}, and RDPMC.
+ */
+ if (!is_guest_mode(vcpu))
+ return kvm_emulate_instruction(vcpu,
+ EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
+
reinject:
kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
return 1;
--
2.53.0.851.ga537e3e6e9-googOn Mon, Mar 16, 2026, Yosry Ahmed wrote:
> +/* Return 0 if not SVM instr, otherwise return associated exit_code */
> +static u64 svm_instr_exit_code(struct kvm_vcpu *vcpu)
To make it very clear what this is doing how about:
static u64 svm_get_decoded_instr_exit_code(struct kvm_vcpu *vcpu)
> {
> struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
>
> if (ctxt->b != 0x1 || ctxt->opcode_len != 2)
> - return NONE_SVM_INSTR;
> + return 0;
This should assert to ensure there's no collision with '0', i.e.
BUILD_BUG_ON(!SVM_EXIT_VMRUN || !SVM_EXIT_VMLOAD || !SVM_EXIT_VMSAVE);
> + if (!is_guest_mode(vcpu))
> + return kvm_emulate_instruction(vcpu,
> + EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
Since you're moving this anyways:
if (!is_guest_mode(vcpu))
return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP |
EMULTYPE_NO_DECODE);
Actually! Better idea, for this code and for the page_address_valid() checks:
invert the checks to reduce indentation, i.e. end up with:
/* FIXME: Handle SVM instructions through the emulator */
svm_exit_code = svm_get_decoded_instr_exit_code(vcpu);
if (svm_exit_code) {
if (!is_guest_mode(vcpu))
return svm_invoke_exit_handler(vcpu, svm_exit_code);
if (nested_svm_check_permissions(vcpu))
return 1;
if (!page_address_valid(vcpu, kvm_register_read(vcpu, VCPU_REGS_RAX)))
goto reinject;
/*
* FIXME: Only synthesize a #VMEXIT if L1 sets the intercept,
* but only after the VMLOAD/VMSAVE exit handlers can properly
* handle VMLOAD/VMSAVE from L2 with VLS enabled in L1 (i.e.
* RAX is an L2 GPA that needs translation through L1's NPT).
*/
nested_svm_simple_vmexit(svm, svm_exit_code);
return 1;
}
/*
* VMware backdoor emulation on #GP interception only handles
* IN{S}, OUT{S}, and RDPMC, and only for L1.
*/
if (!enable_vmware_backdoor || is_guest_mode(vcpu))
goto reinject;
return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
> +
> reinject:
> kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
> return 1;
> --
> 2.53.0.851.ga537e3e6e9-goog
>
On Fri, Apr 3, 2026 at 11:18 AM Sean Christopherson <seanjc@google.com> wrote:
>
> On Mon, Mar 16, 2026, Yosry Ahmed wrote:
> > +/* Return 0 if not SVM instr, otherwise return associated exit_code */
> > +static u64 svm_instr_exit_code(struct kvm_vcpu *vcpu)
>
> To make it very clear what this is doing how about:
>
> static u64 svm_get_decoded_instr_exit_code(struct kvm_vcpu *vcpu)
Yeah I like this better.
>
> > {
> > struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
> >
> > if (ctxt->b != 0x1 || ctxt->opcode_len != 2)
> > - return NONE_SVM_INSTR;
> > + return 0;
>
> This should assert to ensure there's no collision with '0', i.e.
>
> BUILD_BUG_ON(!SVM_EXIT_VMRUN || !SVM_EXIT_VMLOAD || !SVM_EXIT_VMSAVE);
I was gonna add this but I don't think these values can change anyway.
It's good for readability tho so I am fine with it.
>
>
> > + if (!is_guest_mode(vcpu))
> > + return kvm_emulate_instruction(vcpu,
> > + EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
>
> Since you're moving this anyways:
>
> if (!is_guest_mode(vcpu))
> return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP |
> EMULTYPE_NO_DECODE);
>
>
> Actually! Better idea, for this code and for the page_address_valid() checks:
> invert the checks to reduce indentation, i.e. end up with:
>
> /* FIXME: Handle SVM instructions through the emulator */
> svm_exit_code = svm_get_decoded_instr_exit_code(vcpu);
> if (svm_exit_code) {
> if (!is_guest_mode(vcpu))
> return svm_invoke_exit_handler(vcpu, svm_exit_code);
>
> if (nested_svm_check_permissions(vcpu))
> return 1;
>
> if (!page_address_valid(vcpu, kvm_register_read(vcpu, VCPU_REGS_RAX)))
> goto reinject;
>
> /*
> * FIXME: Only synthesize a #VMEXIT if L1 sets the intercept,
> * but only after the VMLOAD/VMSAVE exit handlers can properly
> * handle VMLOAD/VMSAVE from L2 with VLS enabled in L1 (i.e.
> * RAX is an L2 GPA that needs translation through L1's NPT).
> */
> nested_svm_simple_vmexit(svm, svm_exit_code);
> return 1;
> }
>
> /*
> * VMware backdoor emulation on #GP interception only handles
> * IN{S}, OUT{S}, and RDPMC, and only for L1.
> */
> if (!enable_vmware_backdoor || is_guest_mode(vcpu))
> goto reinject;
>
> return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
>
> > +
> > reinject:
> > kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
> > return 1;
The end result looks good to me.
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