x86: Fix the 64-byte boundary enumeration for extended state

The extended state subleaves (EAX=0Dh, ECX=n, n>1).ECX[1]
indicate whether the extended state component locates
on the next 64-byte boundary following the preceding state
component when the compacted format of an XSAVE area is
used.

Right now, they are all zero because no supported component
needed the bit to be set, but the upcoming AMX feature will
use it.  Fix the subleaves value according to KVM's supported
cpuid.

Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220217060434.52460-2-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.c

@@ -5488,6 +5488,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
                 const ExtSaveArea *esa = &x86_ext_save_areas[count];
                 *eax = esa->size;
                 *ebx = esa->offset;
+                *ecx = esa->ecx & ESA_FEATURE_ALIGN64_MASK;
             }
         }
         break;

target/i386/cpu.h

@@ -550,6 +550,11 @@ typedef enum X86Seg {
 #define XSTATE_Hi16_ZMM_MASK            (1ULL << XSTATE_Hi16_ZMM_BIT)
 #define XSTATE_PKRU_MASK                (1ULL << XSTATE_PKRU_BIT)
 
+#define ESA_FEATURE_ALIGN64_BIT         1
+
+#define ESA_FEATURE_ALIGN64_MASK        (1U << ESA_FEATURE_ALIGN64_BIT)
+
+
 /* CPUID feature words */
 typedef enum FeatureWord {
     FEAT_1_EDX,         /* CPUID[1].EDX */
@@ -1356,6 +1361,7 @@ QEMU_BUILD_BUG_ON(sizeof(XSavePKRU) != 0x8);
 typedef struct ExtSaveArea {
     uint32_t feature, bits;
     uint32_t offset, size;
+    uint32_t ecx;
 } ExtSaveArea;
 
 #define XSAVE_STATE_AREA_COUNT (XSTATE_PKRU_BIT + 1)

target/i386/kvm/kvm-cpu.c

@@ -104,6 +104,7 @@ static void kvm_cpu_xsave_init(void)
             if (sz != 0) {
                 assert(esa->size == sz);
                 esa->offset = kvm_arch_get_supported_cpuid(s, 0xd, i, R_EBX);
+                esa->ecx = kvm_arch_get_supported_cpuid(s, 0xd, i, R_ECX);
             }
         }
     }