From: tip-bot for Sebastian Andrzej Siewior <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: bp@alien8.de, tglx@linutronix.de, hpa@zytor.com,
dave.hansen@linux.intel.com, torvalds@linux-foundation.org,
peterz@infradead.org, linux-kernel@vger.kernel.org,
luto@kernel.org, mingo@kernel.org, bigeasy@linutronix.de
Subject: [tip:x86/urgent] x86/fpu: Fix i486 + no387 boot crash by only saving FPU registers on context switch if there is an FPU
Date: Wed, 17 Oct 2018 23:22:54 -0700 [thread overview]
Message-ID: <tip-2224d616528194b02424c91c2ee254b3d29942c3@git.kernel.org> (raw)
In-Reply-To: <20181016202525.29437-4-bigeasy@linutronix.de>
Commit-ID: 2224d616528194b02424c91c2ee254b3d29942c3
Gitweb: https://git.kernel.org/tip/2224d616528194b02424c91c2ee254b3d29942c3
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Tue, 16 Oct 2018 22:25:25 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 17 Oct 2018 12:30:38 +0200
x86/fpu: Fix i486 + no387 boot crash by only saving FPU registers on context switch if there is an FPU
Booting an i486 with "no387 nofxsr" ends with with the following crash:
math_emulate: 0060:c101987d
Kernel panic - not syncing: Math emulation needed in kernel
on the first context switch in user land.
The reason is that copy_fpregs_to_fpstate() tries FNSAVE which does not work
as the FPU is turned off.
This bug was introduced in:
f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active")
Add a check for X86_FEATURE_FPU before trying to save FPU registers (we
have such a check in switch_fpu_finish() already).
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active")
Link: http://lkml.kernel.org/r/20181016202525.29437-4-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.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 a38bf5a1e37a..69dcdf195b61 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -528,7 +528,7 @@ static inline void fpregs_activate(struct fpu *fpu)
static inline void
switch_fpu_prepare(struct fpu *old_fpu, int cpu)
{
- if (old_fpu->initialized) {
+ if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) {
if (!copy_fpregs_to_fpstate(old_fpu))
old_fpu->last_cpu = -1;
else
prev parent reply other threads:[~2018-10-18 6:23 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-16 20:25 [0/3] A few 32bit x86 fixes Sebastian Andrzej Siewior
2018-10-16 20:25 ` [PATCH 1/3] x86/mm/pat: Disable preemption around __flush_tlb_all() Sebastian Andrzej Siewior
2018-10-16 21:25 ` Andy Lutomirski
2018-10-16 21:38 ` Sebastian Andrzej Siewior
2018-10-16 23:28 ` Andy Lutomirski
2018-10-17 10:34 ` [PATCH 1/3 v2] " Sebastian Andrzej Siewior
2018-10-29 18:10 ` [tip:x86/urgent] " tip-bot for Sebastian Andrzej Siewior
2018-11-05 21:56 ` Dan Williams
2018-10-17 9:54 ` [PATCH 1/3] " David Laight
2018-10-17 10:39 ` 'Sebastian Andrzej Siewior'
2018-10-17 11:45 ` David Laight
2018-10-17 12:00 ` 'Sebastian Andrzej Siewior'
2018-10-17 11:11 ` Peter Zijlstra
2018-10-17 11:17 ` Thomas Gleixner
2018-10-17 15:47 ` Peter Zijlstra
2018-10-17 15:55 ` Thomas Gleixner
2018-10-17 16:00 ` 'Sebastian Andrzej Siewior'
2018-10-17 16:22 ` Peter Zijlstra
2018-10-16 20:25 ` [PATCH 2/3] x86/fpu: Remove second definition of fpu in __fpu__restore_sig() Sebastian Andrzej Siewior
2018-10-16 21:26 ` Andy Lutomirski
2018-10-17 9:09 ` [tip:x86/urgent] " tip-bot for Sebastian Andrzej Siewior
2018-10-18 6:22 ` tip-bot for Sebastian Andrzej Siewior
2018-10-16 20:25 ` [PATCH 3/3] x86/fpu: Save FPU registers on context switch if there is a FPU Sebastian Andrzej Siewior
2018-10-16 23:00 ` Andy Lutomirski
2018-10-17 9:10 ` [tip:x86/urgent] x86/fpu: Fix i486 + no387 boot crash by only saving FPU registers on context switch if there is an FPU tip-bot for Sebastian Andrzej Siewior
2018-10-18 6:22 ` tip-bot for Sebastian Andrzej Siewior [this message]
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