x86/vmx: Correct the long mode check in vmx_cpuid_intercept()

%cs.L may be set in a legacy mode segment, or clear in a compatibility mode
segment; it is not the correct way to check for long mode being active.

Both of these situations result in incorrect visibility of the SYSCALL feature
in CPUID, and by extension, incorrect behaviour in hvm_efer_valid().

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <JBeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 9a8f69471b5af25df91708307a9e972d1eb76bc0..a18db28f6f2d4ffc0f0a04d7ebf862f10515db1b 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2407,7 +2407,6 @@ static void vmx_cpuid_intercept(
     unsigned int *ecx, unsigned int *edx)
 {
     unsigned int input = *eax;
-    struct segment_register cs;
     struct vcpu *v = current;
 
     hvm_cpuid(input, eax, ebx, ecx, edx);
@@ -2416,8 +2415,7 @@ static void vmx_cpuid_intercept(
     {
         case 0x80000001:
             /* SYSCALL is visible iff running in long mode. */
-            vmx_get_segment_register(v, x86_seg_cs, &cs);
-            if ( cs.attr.fields.l )
+            if ( hvm_long_mode_enabled(v) )
                 *edx |= cpufeat_mask(X86_FEATURE_SYSCALL);
             else
                 *edx &= ~(cpufeat_mask(X86_FEATURE_SYSCALL));