x86/fpu: Rename xsave.header::xstate_bv to 'xfeatures'

'xsave.header::xstate_bv' is a misnomer - what does 'bv' stand for?

It probably comes from the 'XGETBV' instruction name, but I could
not find in the Intel documentation where that abbreviation comes
from. It could mean 'bit vector' - or something else?

But how about - instead of guessing about a weird name - we named
the field in an obvious and descriptive way that tells us exactly
what it does?

So rename it to 'xfeatures', which is a bitmask of the
xfeatures that are fpstate_active in that context structure.

Eyesore like:

           fpu->state->xsave.xsave_hdr.xstate_bv |= XSTATE_FP;

is now much more readable:

           fpu->state->xsave.header.xfeatures |= XSTATE_FP;

Which form is not just infinitely more readable, but is also
shorter as well.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/include/uapi/asm/sigcontext.h b/arch/x86/include/uapi/asm/sigcontext.h
index 7f850f7..0e8a973 100644
--- a/arch/x86/include/uapi/asm/sigcontext.h
+++ b/arch/x86/include/uapi/asm/sigcontext.h
@@ -25,7 +25,7 @@ struct _fpx_sw_bytes {
 	__u32 extended_size;	/* total size of the layout referred by
 				 * fpstate pointer in the sigcontext.
 				 */
-	__u64 xstate_bv;
+	__u64 xfeatures;
 				/* feature bit mask (including fp/sse/extended
 				 * state) that is present in the memory
 				 * layout.
@@ -210,7 +210,7 @@ struct sigcontext {
 #endif /* !__i386__ */
 
 struct _header {
-	__u64 xstate_bv;
+	__u64 xfeatures;
 	__u64 reserved1[2];
 	__u64 reserved2[5];
 };