x86/svm: Add Enumerations for the SVM virtual NMI

Introduce the cpuid bit for the SVM vNMI feature support for the x86\AMD
platforms. The feature support is indicated by the CPUID
Fn8000_000A_EDX[25] = 1.

Add defines for the three SVM's Virtual NMI (vNMI) managements bits in the
VMCB structure's vintr_t:

vintr_t(11) - Virtual NMI is pending.
vintr_t(12) - Virtual NMI is masked.
vintr_t(26) - Enable NMI virtualization.

Signed-off-by: Abdelkareem Abdelsaamad <abdelkareem.abdelsaamad@citrix.com>
Reviewed-by: Teddy Astie <teddy.astie@vates.tech>
Acked-by: Jan Beulich <jbeulich@suse.com>
master commit: 0294292b4c
master date: 2026-02-23 08:41:32 +0100

xen/arch/x86/include/asm/hvm/svm/svm.h

@@ -37,6 +37,7 @@ extern u32 svm_feature_flags;
 #define SVM_FEATURE_VGIF          16 /* Virtual GIF */
 #define SVM_FEATURE_SSS           19 /* NPT Supervisor Shadow Stacks */
 #define SVM_FEATURE_SPEC_CTRL     20 /* MSR_SPEC_CTRL virtualisation */
+#define SVM_FEATURE_VNMI          25 /* Virtual NMI */
 
 static inline bool cpu_has_svm_feature(unsigned int feat)
 {
@@ -56,5 +57,6 @@ static inline bool cpu_has_svm_feature(unsigned int feat)
 #define cpu_has_svm_vloadsave cpu_has_svm_feature(SVM_FEATURE_VLOADSAVE)
 #define cpu_has_svm_sss       cpu_has_svm_feature(SVM_FEATURE_SSS)
 #define cpu_has_svm_spec_ctrl cpu_has_svm_feature(SVM_FEATURE_SPEC_CTRL)
+#define cpu_has_svm_vnmi      cpu_has_svm_feature(SVM_FEATURE_VNMI)
 
 #endif /* __ASM_X86_HVM_SVM_H__ */

xen/arch/x86/include/asm/hvm/svm/vmcb.h

@@ -338,13 +338,17 @@ typedef union
         u64 tpr:          8;
         u64 irq:          1;
         u64 vgif:         1;
-        u64 rsvd0:        6;
+        u64 :             1;
+        u64 vnmi_pending: 1;
+        u64 vnmi_blocking:1;
+        u64 :             3;
         u64 prio:         4;
         u64 ign_tpr:      1;
         u64 rsvd1:        3;
         u64 intr_masking: 1;
         u64 vgif_enable:  1;
-        u64 rsvd2:        6;
+        u64 vnmi_enable:  1;
+        u64 :             5;
         u64 vector:       8;
         u64 rsvd3:       24;
     } fields;