[xen stable-4.12] x86: determine MXCSR mask in all cases

[patchbot@xxxxxxx]

commit b3af150fd42ed0a0723115063c028f21feab348a
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Jun 24 17:01:10 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jun 24 17:01:10 2020 +0200

    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@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 2b532519d64e653a6bbfd9eefed6040a09c8876d
    master date: 2020-05-18 17:18:56 +0200
---
 xen/arch/x86/cpu/common.c |  3 +--
 xen/arch/x86/xstate.c     | 18 ++++++++++++------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 851c23ddc5..f3a8c69020 100644
--- 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 858d1a6573..1469292d27 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -584,6 +584,18 @@ 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 )
     {
@@ -607,8 +619,6 @@ 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.
@@ -617,10 +627,6 @@ 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
     {
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12