[Xen-changelog] [xen-unstable] hvm: fix XSAVE leaf 0 EBX size calculation

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1297013191 0
# Node ID 7ada6faef565bd8f676ddfaff9c568ca592ee5be
# Parent  575d2f40acc4b2ac1528efe023c4e66914efdb8b
hvm: fix XSAVE leaf 0 EBX size calculation

Fixes a size calculation bug when enabled bits in XFEATURE_MASK (xcr0)
aren't contiguous.

Current for_loop will stop when xcr0 feature bit is 0. But in reality,
the bits can be non-contiguous. One example is that LWP is bit 62 on
AMD platform. This patch iterates through all bits to calculate the
size for enabled features.

Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
---
 xen/arch/x86/hvm/hvm.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff -r 575d2f40acc4 -r 7ada6faef565 xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c    Sun Feb 06 17:22:44 2011 +0000
+++ b/xen/arch/x86/hvm/hvm.c    Sun Feb 06 17:26:31 2011 +0000
@@ -2222,10 +2222,12 @@ void hvm_cpuid(unsigned int input, unsig
         /* EBX value of main leaf 0 depends on enabled xsave features */
         if ( count == 0 && v->arch.xcr0 ) 
         {
-            for ( sub_leaf = 2; 
-                  (sub_leaf < 64) && (v->arch.xcr0 & (1ULL << sub_leaf));
-                  sub_leaf++ ) 
+            /* reset EBX to default value first */
+            *ebx = 576; 
+            for ( sub_leaf = 2; sub_leaf < 64; sub_leaf++ )
             {
+                if ( !(v->arch.xcr0 & (1ULL << sub_leaf)) )
+                    continue;
                 domain_cpuid(v->domain, input, sub_leaf, &_eax, &_ebx, &_ecx, 
                              &_edx);
                 if ( (_eax + _ebx) > *ebx )

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