kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule

CPUID.0xD.1.EBX enumerates the size of the XSAVE area (in compacted
format) required by XSAVES. If CPUID.0xD.i.ECX[1] is set for a state
component (i), this state component should be located on the next
64-bytes boundary following the preceding state component in the
compacted layout.

Fix xstate_required_size() to follow the alignment rule. AMX is the
first state component with 64-bytes alignment to catch this bug.

Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220105123532.12586-4-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 0b920e1..f3e6fda 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -42,7 +42,11 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
                if (xstate_bv & 0x1) {
                        u32 eax, ebx, ecx, edx, offset;
                        cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
-                       offset = compacted ? ret : ebx;
+                       /* ECX[1]: 64B alignment in compacted form */
+                       if (compacted)
+                               offset = (ecx & 0x2) ? ALIGN(ret, 64) : ret;
+                       else
+                               offset = ebx;
                        ret = max(ret, offset + eax);
                }