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From: Andy Lutomirski <luto@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andrew Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@alien8.de>, stable <stable@vger.kernel.org>
Subject: Re: [PATCH 3/3] x86/fpu: Save FPU registers on context switch if there is a FPU
Date: Tue, 16 Oct 2018 16:00:23 -0700	[thread overview]
Message-ID: <CALCETrV2jEG1b7deGeyxwRrXLk30Q2nn6hstzeTpE80i+vu1mQ@mail.gmail.com> (raw)
In-Reply-To: <20181016202525.29437-4-bigeasy@linutronix.de>

On Tue, Oct 16, 2018 at 1:25 PM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> 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>

Reviewed-by: Andy Lutomirski <luto@kernel.org>

  reply	other threads:[~2018-10-16 23:00 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 [this message]
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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