x86: determine MXCSR mask in all cases

For its use(s) by the emulator to be correct in all cases, the filling
of the variable needs to be independent of XSAVE availability. As
there's no suitable function in i387.c to put the logic in, keep it in
xstate_init(), arrange for the function to be called unconditionally,
and pull the logic ahead of all return paths there.

Fixes: 9a4496a35b20 ("x86emul: support {,V}{LD,ST}MXCSR")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 63f3893c7a6d437d41765d8bb9fcc51e17653202..3e0d9cbe986e771417760546c0bad4dca2f36ec6 100644 (file)
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -488,8 +488,7 @@ void identify_cpu(struct cpuinfo_x86 *c)
 
        /* Now the feature flags better reflect actual CPU features! */
 
-       if ( cpu_has_xsave )
-               xstate_init(c);
+       xstate_init(c);
 
 #ifdef NOISY_CAPS
        printk(KERN_DEBUG "CPU: After all inits, caps:");

diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index 078419a1712f0bb562824bfd4082ccdd74415917..3794d9a5a54397fb14d20cd1580b5c5b85c63c17 100644 (file)
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -588,6 +588,18 @@ void xstate_init(struct cpuinfo_x86 *c)
     u32 eax, ebx, ecx, edx;
     u64 feature_mask;
 
+    if ( bsp )
+    {
+        static typeof(current->arch.xsave_area->fpu_sse) __initdata ctxt;
+
+        asm ( "fxsave %0" : "=m" (ctxt) );
+        if ( ctxt.mxcsr_mask )
+            mxcsr_mask = ctxt.mxcsr_mask;
+    }
+
+    if ( !cpu_has_xsave )
+        return;
+
     if ( (bsp && !use_xsave) ||
          boot_cpu_data.cpuid_level < XSTATE_CPUID )
     {
@@ -611,8 +623,6 @@ void xstate_init(struct cpuinfo_x86 *c)
 
     if ( bsp )
     {
-        static typeof(current->arch.xsave_area->fpu_sse) __initdata ctxt;
-
         xfeature_mask = feature_mask;
         /*
          * xsave_cntxt_size is the max size required by enabled features.
@@ -621,10 +631,6 @@ void xstate_init(struct cpuinfo_x86 *c)
         xsave_cntxt_size = _xstate_ctxt_size(feature_mask);
         printk("xstate: size: %#x and states: %#"PRIx64"\n",
                xsave_cntxt_size, xfeature_mask);
-
-        asm ( "fxsave %0" : "=m" (ctxt) );
-        if ( ctxt.mxcsr_mask )
-            mxcsr_mask = ctxt.mxcsr_mask;
     }
     else
     {