x86/fpu: Make XSAVE check the base CPUID features before enabling

Before enabling XSAVE, not only check the XSAVE specific CPUID bits,
but also the base CPUID features of the respective XSAVE feature.
This allows to disable individual XSAVE states using the existing
clearcpuid= option, which can be useful for performance testing
and debugging, and also in general avoids inconsistencies.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171013215645.23166-5-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index f1d5476c9022..fb581292975b 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -15,6 +15,7 @@
 #include <asm/fpu/xstate.h>
 
 #include <asm/tlbflush.h>
+#include <asm/cpufeature.h>
 
 /*
  * Although we spell it out in here, the Processor Trace
@@ -36,6 +37,19 @@ static const char *xfeature_names[] =
         "unknown xstate feature"        ,
 };
 
+static short xsave_cpuid_features[] __initdata = {
+        X86_FEATURE_FPU,
+        X86_FEATURE_XMM,
+        X86_FEATURE_AVX,
+        X86_FEATURE_MPX,
+        X86_FEATURE_MPX,
+        X86_FEATURE_AVX512F,
+        X86_FEATURE_AVX512F,
+        X86_FEATURE_AVX512F,
+        X86_FEATURE_INTEL_PT,
+        X86_FEATURE_PKU,
+};
+
 /*
  * Mask of xstate features supported by the CPU and the kernel:
  */
@@ -726,6 +740,7 @@ void __init fpu__init_system_xstate(void)
         unsigned int eax, ebx, ecx, edx;
         static int on_boot_cpu __initdata = 1;
         int err;
+        int i;
 
         WARN_ON_FPU(!on_boot_cpu);
         on_boot_cpu = 0;
@@ -759,6 +774,14 @@ void __init fpu__init_system_xstate(void)
                 goto out_disable;
         }
 
+        /*
+         * Clear XSAVE features that are disabled in the normal CPUID.
+         */
+        for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
+                if (!boot_cpu_has(xsave_cpuid_features[i]))
+                        xfeatures_mask &= ~BIT(i);
+        }
+
         xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 
         /* Enable xstate instructions to be able to continue with initialization: */