On Tue, 2018-10-02 at 19:15 +0200, Borislav Petkov wrote:

On Fri, Sep 21, 2018 at 08:03:27AM -0700, Yu-cheng Yu wrote:

quoted

diff --git a/arch/x86/include/asm/fpu/xstate.h

b/arch/x86/include/asm/fpu/xstate.h
index 9b382e5157ed..a32dc5f8c963 100644

--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h

@@ -19,10 +19,10 @@
 #define XSAVE_YMM_SIZE	    256
 #define XSAVE_YMM_OFFSET    (XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET)
 
-/* System features */
-#define XFEATURE_MASK_SYSTEM (XFEATURE_MASK_PT)

Previous patch renames it, this patch deletes it. Why do we need all
that unnecessary churn?

Also, this patch is trying to do a couple of things at once and
reviewing it is not trivial. Please split the changes logically.

Yes, if we leave XFEATURE_MASK_SUPERVISOR unchanged in the previous patch, this
patch becomes much simpler.  Perhaps we don't even need to split this one.

quoted

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 19f8df54c72a..dd2c561c4544 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c

@@ -51,13 +51,16 @@ static short xsave_cpuid_features[] __initdata = {
 };
 
 /*
- * Mask of xstate features supported by the CPU and the kernel:
+ * Mask of xstate features supported by the CPU and the kernel.
+ * This is the result from CPUID query, SUPPORTED_XFEATURES_MASK,
+ * and boot_cpu_has().
  */

This needs to explain what both masks are - user and system. "CPU" and
"kernel" is not "user" and "all".

quoted

 u64 xfeatures_mask_user __read_mostly;
+u64 xfeatures_mask_all __read_mostly;

The first one is all supported "user" states; the latter is "system" and "user"
states combined.  I will put in comments.

Yu-cheng