[Xen-devel] [PATCH] x86: reduce magic number usage in XSAVE code (RE: [PATCH][HVM] fix XSAVE leaf 0 EBX size calculation)

["Wei, Gang" <gang.wei@xxxxxxxxx>]

Wei Huang wrote onÂ2011-02-05:
> 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>

ACK on the patch despite it was checked in already. BTW, I want to add a 
trivial patch to limit the magic number usage in XSAVE code.

x86: reduce magic number usage in XSAVE code

Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>

diff -r aeda4adecaf8 xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c    Tue Feb 08 16:35:35 2011 +0000
+++ b/xen/arch/x86/hvm/hvm.c    Thu Feb 10 19:12:29 2011 +0800
@@ -2223,7 +2223,7 @@ void hvm_cpuid(unsigned int input, unsig
         if ( count == 0 && v->arch.xcr0 ) 
         {
             /* reset EBX to default value first */
-            *ebx = 576; 
+            *ebx = XSAVE_AREA_MIN_SIZE; 
             for ( sub_leaf = 2; sub_leaf < 64; sub_leaf++ )
             {
                 if ( !(v->arch.xcr0 & (1ULL << sub_leaf)) )
diff -r aeda4adecaf8 xen/arch/x86/i387.c
--- a/xen/arch/x86/i387.c       Tue Feb 08 16:35:35 2011 +0000
+++ b/xen/arch/x86/i387.c       Thu Feb 10 19:14:02 2011 +0800
@@ -221,7 +221,6 @@ static void restore_fpu(struct vcpu *v)
 }
 
 #define XSTATE_CPUID 0xd
-#define XSAVE_AREA_MIN_SIZE (512 + 64) /* FP/SSE + XSAVE.HEADER */
 
 /*
  * Maximum size (in byte) of the XSAVE/XRSTOR save area required by all
diff -r aeda4adecaf8 xen/include/asm-x86/i387.h
--- a/xen/include/asm-x86/i387.h        Tue Feb 08 16:35:35 2011 +0000
+++ b/xen/include/asm-x86/i387.h        Thu Feb 10 19:11:37 2011 +0800
@@ -21,13 +21,14 @@ int xsave_alloc_save_area(struct vcpu *v
 int xsave_alloc_save_area(struct vcpu *v);
 void xsave_free_save_area(struct vcpu *v);
 
+#define XSAVE_AREA_MIN_SIZE (512 + 64) /* FP/SSE + XSAVE.HEADER */
 #define XSTATE_FP       (1ULL << 0)
 #define XSTATE_SSE      (1ULL << 1)
 #define XSTATE_YMM      (1ULL << 2)
 #define XSTATE_LWP      (1ULL << 62) /* AMD lightweight profiling */
 #define XSTATE_FP_SSE   (XSTATE_FP | XSTATE_SSE)
 #define XCNTXT_MASK     (XSTATE_FP | XSTATE_SSE | XSTATE_YMM | XSTATE_LWP)
-#define XSTATE_YMM_OFFSET  (512 + 64)
+#define XSTATE_YMM_OFFSET  XSAVE_AREA_MIN_SIZE
 #define XSTATE_YMM_SIZE    256
 #define XSAVEOPT        (1 << 0)


Jimmy

Attachment: xsave_trivial_change.patch
Description: xsave_trivial_change.patch

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