linux-kernel - [PATCH 23/33] x86/fpu: Turn WARN_ON() in context switch into WARN_ON

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Message-Id: <20170923130016.21448-24-mingo@kernel.org>
Date:   Sat, 23 Sep 2017 15:00:06 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biggers <ebiggers3@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH 23/33] x86/fpu: Turn WARN_ON() in context switch into WARN_ON_FPU()

From: Andi Kleen <ak@...ux.intel.com>

copy_xregs_to_kernel checks if the alternatives have been already
patched.

This WARN_ON() is always executed in every context switch.

All the other checks in fpu internal.h are WARN_ON_FPU(), but
this one is plain WARN_ON(). I assume it was forgotten to switch it.

So switch it to WARN_ON_FPU() too to avoid some unnecessary code
in the context switch, and a potentially expensive cache line miss for the
global variable.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20170329062605.4970-1-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/fpu/internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 629e7abcd6c9..2dca7c65319c 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -350,7 +350,7 @@ static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
 	u32 hmask = mask >> 32;
 	int err;
 
-	WARN_ON(!alternatives_patched);
+	WARN_ON_FPU(!alternatives_patched);
 
 	XSTATE_XSAVE(xstate, lmask, hmask, err);
 
-- 
2.11.0