[RFC PATCH 1/7] x86: Fix the 64-byte boundary enumeration for extended state

[Yang Zhong]

From: Jing Liu <jing2.liu@intel.com>

The extended state subleaves (EAX=0Dh, ECX=n, n>1).ECX[1]
are all zero, while spec actually introduces that bit 01
should indicate if 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.

Fix the subleaves value according to the host supported
cpuid. The upcoming AMX feature would be the first one
using it.

Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
---
 target/i386/cpu.h         | 1 +
 target/i386/cpu.c         | 1 +
 target/i386/kvm/kvm-cpu.c | 3 +++
 3 files changed, 5 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 04f2b790c9..7f9700544f 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1354,6 +1354,7 @@ QEMU_BUILD_BUG_ON(sizeof(XSavePKRU) != 0x8);
 typedef struct ExtSaveArea {
     uint32_t feature, bits;
     uint32_t offset, size;
+    uint32_t need_align;
 } ExtSaveArea;
 
 #define XSAVE_STATE_AREA_COUNT (XSTATE_PKRU_BIT + 1)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index aa9e636800..47bc4d5c1a 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5487,6 +5487,7 @@ 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->need_align << 1;
             }
         }
         break;
diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
index d95028018e..6c4c1c6f9d 100644
--- a/target/i386/kvm/kvm-cpu.c
+++ b/target/i386/kvm/kvm-cpu.c
@@ -105,6 +105,9 @@ static void kvm_cpu_xsave_init(void)
                 assert(esa->size == sz);
                 esa->offset = kvm_arch_get_supported_cpuid(s, 0xd, i, R_EBX);
             }
+
+            uint32_t ecx = kvm_arch_get_supported_cpuid(s, 0xd, i, R_ECX);
+            esa->need_align = ecx & (1u << 1) ? 1 : 0;
         }
     }
 }