From: Borislav Petkov <bp@alien8.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>, Borislav Petkov <bp@suse.de>
Subject: [PATCH] x86, FPU: Fix FPU initialization
Date: Wed, 10 Apr 2013 23:29:50 +0200 [thread overview]
Message-ID: <20130410212950.GA6899@pd.tnic> (raw)
In-Reply-To: <20130410161122.GI6857@pd.tnic>
On Wed, Apr 10, 2013 at 06:11:22PM +0200, Borislav Petkov wrote:
> On Wed, Apr 10, 2013 at 08:35:43AM -0700, H. Peter Anvin wrote:
> > OK, this thread took off in another direction but you're still looking
> > at this, right?
>
> Yep, and I think I have the rootcause, let's start (oops below for
> info).
Ok, here's a fix which boots fine here in qemu. Ingo, it would be cool
if you gave it a run to verify.
Thanks.
--
>From 2263430417dd8de1a5fef4b2c40127e681fdc1ab Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@suse.de>
Date: Wed, 10 Apr 2013 21:37:03 +0200
Subject: [PATCH] x86, FPU: Fix FPU initialization
c70293d0e3fe ("x86: Get rid of ->hard_math and all the FPU asm
fu") converted the FPU detection code to C. Yours truly, in his
overzealousness, used static_cpu_has() too early, before alternatives
have run, leading to the checks in fpu_init() to fail and fpu_init() to
set CR0.EM.
This, in turn, lead to an early NULL ptr due to
a chicken-and-an-egg issue (full details here:
http://lkml.kernel.org/r/20130410161122.GI6857@pd.tnic).
Fix it back to the normal CPU feature checks.
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/i387.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 3a6455304c8d..b0928898bf54 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -163,7 +163,7 @@ void __cpuinit fpu_init(void)
unsigned long cr4_mask = 0;
#ifndef CONFIG_MATH_EMULATION
- if (!static_cpu_has(X86_FEATURE_FPU)) {
+ if (!cpu_has_fpu) {
pr_emerg("No FPU found and no math emulation present\n");
pr_emerg("Giving up\n");
for (;;)
@@ -179,7 +179,7 @@ void __cpuinit fpu_init(void)
cr0 = read_cr0();
cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
- if (!static_cpu_has(X86_FEATURE_FPU))
+ if (!cpu_has_fpu)
cr0 |= X86_CR0_EM;
write_cr0(cr0);
--
1.8.2.135.g7b592fa
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
next prev parent reply other threads:[~2013-04-10 21:29 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-08 15:57 [PATCH 0/4] x86: FPU detection in C Borislav Petkov
2013-04-08 15:57 ` [PATCH 1/4] x86: Get rid of ->hard_math and all the FPU asm fu Borislav Petkov
2013-04-08 16:26 ` [tip:x86/cpu] " tip-bot for H. Peter Anvin
2013-06-12 20:48 ` [tip:x86/fpu] " tip-bot for H. Peter Anvin
2013-04-08 15:57 ` [PATCH 2/4] x86: Fold-in trivial check_config function Borislav Petkov
2013-04-08 16:27 ` [tip:x86/cpu] " tip-bot for Borislav Petkov
2013-04-16 13:51 ` tip-bot for Borislav Petkov
2013-04-08 15:57 ` [PATCH 3/4] x86, AMD: Correct {rd,wr}msr_amd_safe warnings Borislav Petkov
2013-04-08 16:28 ` [tip:x86/cpu] " tip-bot for Borislav Petkov
2013-04-16 13:53 ` tip-bot for Borislav Petkov
2013-04-08 15:57 ` [PATCH 4/4] x86, CPU, AMD: Drop useless label Borislav Petkov
2013-04-08 16:29 ` [tip:x86/cpu] " tip-bot for Borislav Petkov
2013-04-16 13:54 ` tip-bot for Borislav Petkov
2013-04-10 11:08 ` [PATCH 0/4] x86: FPU detection in C Ingo Molnar
2013-04-10 12:24 ` Borislav Petkov
2013-04-10 12:25 ` Ingo Molnar
2013-04-10 13:32 ` Borislav Petkov
2013-04-10 15:35 ` H. Peter Anvin
2013-04-10 16:11 ` Borislav Petkov
2013-04-10 21:29 ` Borislav Petkov [this message]
2013-04-11 12:09 ` [PATCH] x86, FPU: Fix FPU initialization Ingo Molnar
2013-04-11 14:23 ` Borislav Petkov
2013-04-11 19:26 ` H. Peter Anvin
2013-04-11 20:23 ` Borislav Petkov
2013-04-12 5:32 ` Ingo Molnar
2013-04-12 5:34 ` H. Peter Anvin
2013-04-12 9:47 ` Borislav Petkov
2013-04-12 11:26 ` Borislav Petkov
2013-04-15 10:08 ` Ingo Molnar
2013-04-15 10:17 ` Borislav Petkov
2013-04-15 10:18 ` Ingo Molnar
2013-04-15 15:54 ` Borislav Petkov
2013-04-15 22:04 ` Borislav Petkov
2013-04-16 9:25 ` Ingo Molnar
2013-04-16 9:48 ` Borislav Petkov
2013-04-16 10:08 ` [GIT PULL] Rebase tip:x86/cpu Borislav Petkov
2013-04-16 11:35 ` Ingo Molnar
2013-04-16 11:33 ` [PATCH] x86, FPU: Fix FPU initialization Ingo Molnar
2013-04-29 14:04 [PATCH 0/3] FPU detection in C, second try Borislav Petkov
2013-04-29 14:04 ` [PATCH 1/3] x86: Get rid of ->hard_math and all the FPU asm fu Borislav Petkov
2013-04-29 14:04 ` [PATCH 2/3] x86: Sanity-check static_cpu_has usage Borislav Petkov
2013-04-29 15:38 ` H. Peter Anvin
2013-04-29 14:04 ` [PATCH 3/3] x86, FPU: Do not use static_cpu_has before alternatives Borislav Petkov
2013-04-29 15:42 ` H. Peter Anvin
2013-04-29 18:51 ` Borislav Petkov
2013-04-29 18:58 ` H. Peter Anvin
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