[xen stable-4.13] x86: determine MXCSR mask in all cases

[patchbot@xxxxxxx]

commit 7f6b66d71ff7ef5695da15b1e4b3ee7e0fc5140d
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Jun 24 16:27:55 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jun 24 16:27:55 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 e5ad17d8d9..ad34d9b526 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -487,8 +487,7 @@ 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 243495ed07..0abf20d2ef 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -587,6 +587,18 @@ 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 )
     {
@@ -610,8 +622,6 @@ 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.
@@ -620,10 +630,6 @@ 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-4.13