[Xen-changelog] [xen stable-4.7] x86/vmx: Correct the long mode check in vmx_cpuid_intercept()

[patchbot@xxxxxxx]

commit d651253049899d2221eea088901cc70a09b3f32c
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Jan 18 10:00:02 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jan 18 10:00:02 2017 +0100

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    master commit: fcb618c025f9251d7e22138f6528595037252c21
    master date: 2016-11-16 10:32:54 +0000
---
 xen/arch/x86/hvm/vmx/vmx.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 385894f..fdd1cd3 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2382,7 +2382,6 @@ 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);
@@ -2391,8 +2390,7 @@ 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));
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7

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