x86/fpu: Disable XSAVES* support for now

[deliverable/linux.git] / arch / x86 / kernel / i387.c

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 009183276bb738fbd28805256ccfaa04e063c364..6185d3141219019d82fa2ea56c4f2f5728b8d17a 100644 (file)
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -173,6 +173,21 @@ static void init_thread_xstate(void)
                xstate_size = sizeof(struct i387_fxsave_struct);
        else
                xstate_size = sizeof(struct i387_fsave_struct);
+
+       /*
+        * Quirk: we don't yet handle the XSAVES* instructions
+        * correctly, as we don't correctly convert between
+        * standard and compacted format when interfacing
+        * with user-space - so disable it for now.
+        *
+        * The difference is small: with recent CPUs the
+        * compacted format is only marginally smaller than
+        * the standard FPU state format.
+        *
+        * ( This is easy to backport while we are fixing
+        *   XSAVES* support. )
+        */
+       setup_clear_cpu_cap(X86_FEATURE_XSAVES);
 }
 
 /*