[Xen-devel] [PATCH] tools/libxc: Correct use of X86_XSS_MASK in guest xstate generation

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

c/s 75f9455e "tools/libxc: Calculate xstate cpuid leaf from guest information"
incorrectly inverted the shift and mask when using X86_XSS_MASK.  Luckily, the
mask is currently zero, avoiding incorrect calculations.

While adjusting this, use an explcit uint32_t cast rather than masking against
0xffffffff.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>

Submitted-from: A punt, on the Cam, during the the hackathon, because.
---
 tools/libxc/xc_cpuid_x86.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index 6d14904..84f4e08 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -460,7 +460,7 @@ static void xc_cpuid_config_xsave(xc_interface *xch,
     {
     case 0:
         /* EAX: low 32bits of xfeature_enabled_mask */
-        regs[0] = guest_xfeature_mask & 0xFFFFFFFF;
+        regs[0] = (uint32_t)guest_xfeature_mask;
         /* EDX: high 32bits of xfeature_enabled_mask */
         regs[3] = guest_xfeature_mask >> 32;
         /* ECX: max size required by all HW features */
@@ -487,8 +487,8 @@ static void xc_cpuid_config_xsave(xc_interface *xch,
 
         if ( test_bit(X86_FEATURE_XSAVES, info->featureset) )
         {
-            regs[2] = guest_xfeature_mask & X86_XSS_MASK & 0xFFFFFFFF;
-            regs[3] = (guest_xfeature_mask >> 32) & X86_XSS_MASK;
+            regs[2] = (uint32_t)(guest_xfeature_mask & X86_XSS_MASK);
+            regs[3] = (guest_xfeature_mask & X86_XSS_MASK) >> 32;
         }
         else
             regs[2] = regs[3] = 0;
-- 
1.9.1


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