From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
stable@vger.kernel.org
Subject: [PATCH 3/3] x86/fpu: Save FPU registers on context switch if there is a FPU
Date: Tue, 16 Oct 2018 22:25:25 +0200 [thread overview]
Message-ID: <20181016202525.29437-4-bigeasy@linutronix.de> (raw)
In-Reply-To: <20181016202525.29437-1-bigeasy@linutronix.de>
Booting a 486 with "no387 nofxsr" ends with
| 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. This
happens since commit 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 switch_fpu_finish() already).
Fixes: f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active")
Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
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 a38bf5a1e37ad..69dcdf195b611 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
--
2.19.1
next prev parent reply other threads:[~2018-10-16 20:26 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 ` Sebastian Andrzej Siewior [this message]
2018-10-16 23:00 ` [PATCH 3/3] x86/fpu: Save FPU registers on context switch if there is a FPU 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
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