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From: Anton Blanchard <anton@ozlabs.org>
To: mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org,
	aneesh.kumar@linux.vnet.ibm.com, acsawdey@linux.vnet.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 2/3] powerpc: Avoid load hit store in setup_sigcontext()
Date: Sun, 29 May 2016 22:03:51 +1000	[thread overview]
Message-ID: <1464523432-12605-2-git-send-email-anton@ozlabs.org> (raw)
In-Reply-To: <1464523432-12605-1-git-send-email-anton@ozlabs.org>

From: Anton Blanchard <anton@samba.org>

In setup_sigcontext(), we set current->thread.vrsave then use it
straight after. Since current is hidden from the compiler via inline
assembly, it cannot optimise this and we end up with a load hit store.

Fix this by using a temporary.

Signed-off-by: Anton Blanchard <anton@samba.org>
---
 arch/powerpc/kernel/signal_64.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 2552079..7e49984 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -104,6 +104,7 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
 	 */
 #ifdef CONFIG_ALTIVEC
 	elf_vrreg_t __user *v_regs = sigcontext_vmx_regs(sc);
+	unsigned long vrsave;
 #endif
 	unsigned long msr = regs->msr;
 	long err = 0;
@@ -125,9 +126,13 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
 	/* We always copy to/from vrsave, it's 0 if we don't have or don't
 	 * use altivec.
 	 */
-	if (cpu_has_feature(CPU_FTR_ALTIVEC))
-		current->thread.vrsave = mfspr(SPRN_VRSAVE);
-	err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
+	vrsave = 0;
+	if (cpu_has_feature(CPU_FTR_ALTIVEC)) {
+		vrsave = mfspr(SPRN_VRSAVE);
+		current->thread.vrsave = vrsave;
+	}
+
+	err |= __put_user(vrsave, (u32 __user *)&v_regs[33]);
 #else /* CONFIG_ALTIVEC */
 	err |= __put_user(0, &sc->v_regs);
 #endif /* CONFIG_ALTIVEC */
-- 
2.7.4

  reply	other threads:[~2016-05-29 12:04 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-29 12:03 [PATCH 1/3] powerpc: Avoid load hit store in __giveup_fpu() and __giveup_altivec() Anton Blanchard
2016-05-29 12:03 ` Anton Blanchard [this message]
2016-05-29 23:14   ` [PATCH 2/3] powerpc: Avoid load hit store in setup_sigcontext() Michael Neuling
2016-05-29 23:23     ` Anton Blanchard
2016-06-15 12:39   ` [2/3] " Michael Ellerman
2016-05-29 12:03 ` [PATCH 3/3] powerpc: Avoid load hit store when using find_linux_pte_or_hugepte() Anton Blanchard
2016-05-30  5:17   ` Aneesh Kumar K.V
2016-05-30 23:29   ` Michael Ellerman
2016-05-31  3:29     ` Aneesh Kumar K.V
2016-05-31  4:18       ` Michael Ellerman
2016-05-31  6:52         ` Aneesh Kumar K.V
2016-06-01  3:43   ` [3/3] " Michael Ellerman
2016-06-01  5:35     ` Anton Blanchard
2016-05-30  8:15 ` [PATCH 1/3] powerpc: Avoid load hit store in __giveup_fpu() and __giveup_altivec() Gabriel Paubert
2016-05-31 10:09   ` Anton Blanchard
2016-06-01  3:06     ` Michael Ellerman
2016-06-15 12:39 ` [1/3] " Michael Ellerman

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