This will be necessary in order to check whether AVX is enabled.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/kvm_emulate.h | 1 +
 arch/x86/kvm/x86.c         | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 83af019620e3..5f9d69c64cd5 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -237,6 +237,7 @@ struct x86_emulate_ops {
 	bool (*is_smm)(struct x86_emulate_ctxt *ctxt);
 	int (*leave_smm)(struct x86_emulate_ctxt *ctxt);
 	void (*triple_fault)(struct x86_emulate_ctxt *ctxt);
+	int (*get_xcr)(struct x86_emulate_ctxt *ctxt, u32 index, u64 *xcr);
 	int (*set_xcr)(struct x86_emulate_ctxt *ctxt, u32 index, u64 xcr);
 
 	gva_t (*get_untagged_addr)(struct x86_emulate_ctxt *ctxt, gva_t addr,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c9c2aa6f4705..cfce7c120215 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8842,6 +8842,14 @@ static void emulator_triple_fault(struct x86_emulate_ctxt *ctxt)
 	kvm_make_request(KVM_REQ_TRIPLE_FAULT, emul_to_vcpu(ctxt));
 }
 
+static int emulator_get_xcr(struct x86_emulate_ctxt *ctxt, u32 index, u64 *xcr)
+{
+	if (index != XCR_XFEATURE_ENABLED_MASK)
+		return 1;
+	*xcr = emul_to_vcpu(ctxt)->arch.xcr0;
+	return 0;
+}
+
 static int emulator_set_xcr(struct x86_emulate_ctxt *ctxt, u32 index, u64 xcr)
 {
 	return __kvm_set_xcr(emul_to_vcpu(ctxt), index, xcr);
@@ -8914,6 +8922,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.is_smm              = emulator_is_smm,
 	.leave_smm           = emulator_leave_smm,
 	.triple_fault        = emulator_triple_fault,
+	.get_xcr             = emulator_get_xcr,
 	.set_xcr             = emulator_set_xcr,
 	.get_untagged_addr   = emulator_get_untagged_addr,
 	.is_canonical_addr   = emulator_is_canonical_addr,
-- 
2.43.5

On 11/13/2025 4:36 PM, Paolo Bonzini wrote:
> This will be necessary in order to check whether AVX is enabled.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Indeed, REX2 emulation support also needs this to check APX. Thanks!

   Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>