[PATCH v1 3/9] KVM: SVM: Set kvm_caps.has_extapic when CPU supports Extended APIC

[Manali Shukla <manali.shukla@amd.com>]

Set kvm_caps.has_extapic when the CPU has X86_FEATURE_EXTAPIC, allowing
KVM to expose Extended APIC functionality to AMD guests.  This is a
prerequisite for advertising AMD's extended APIC space to userspace and
enabling extended LVT emulation.

The has_extapic flag gates access to extended APIC registers (APIC_EFEAT
at 0x400, APIC_ECTRL at 0x410, and APIC_EILVTn at 0x500-0x530) beyond
the standard APIC register space.

Signed-off-by: Manali Shukla <manali.shukla@amd.com>
---
 arch/x86/kvm/svm/svm.c | 3 +++
 arch/x86/kvm/x86.h     | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7803d2781144..6b582fede23d 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5356,6 +5356,9 @@ static __init void svm_set_cpu_caps(void)
 	if (cpu_feature_enabled(X86_FEATURE_BUS_LOCK_THRESHOLD))
 		kvm_caps.has_bus_lock_exit = true;
 
+	if (cpu_feature_enabled(X86_FEATURE_EXTAPIC))
+		kvm_caps.has_extapic = true;
+
 	/* CPUID 0x80000008 */
 	if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) ||
 	    boot_cpu_has(X86_FEATURE_AMD_SSBD))
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 70e81f008030..ec70f6579b58 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -27,6 +27,8 @@ struct kvm_caps {
 	bool has_bus_lock_exit;
 	/* notify VM exit supported? */
 	bool has_notify_vmexit;
+	/* extapic supported */
+	bool has_extapic;
 	/* bit mask of VM types */
 	u32 supported_vm_types;
 
-- 
2.43.0