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

[patchbot@xxxxxxx]

commit fcb618c025f9251d7e22138f6528595037252c21
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Nov 14 10:15:00 2016 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Nov 16 10:32:54 2016 +0000

    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>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 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 9a8f694..a18db28 100644
--- 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));
--
generated by git-patchbot for /home/xen/git/xen.git#master

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