From: Matt Fleming <matt@console-pimps.org>
To: Borislav Petkov <bp@suse.de>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, hpa@zytor.com,
ricardo.neri-calderon@linux.intel.com, tglx@linutronix.de,
matt.fleming@intel.com, linux-tip-commits@vger.kernel.org,
Seiji Aguchi <seiji.aguchi@hds.com>
Subject: Re: [tip:x86/efi] x86/efi: Save and restore FPU context around efi_calls (x86_64)
Date: Fri, 25 Apr 2014 12:09:36 +0100 [thread overview]
Message-ID: <20140425110936.GB26088@console-pimps.org> (raw)
In-Reply-To: <20140420002811.GA18663@pd.tnic>
On Sun, 20 Apr, at 02:28:11AM, Borislav Petkov wrote:
>
> I guess you can use the kernel_fpu_begin/end() variants here (i.e.,
> without the "__") which disable and enable preemption and thus drop the
> preempt_* calls:
>
> efi_sync_low_kernel_mappings();
> kernel_fpu_begin();
> __s = efi_call((void *)efi.systab->runtime->f, __VA_ARGS__);
> kernel_fpu_end();
> __s;
>
> I'm not sure about the
>
> WARN_ON_ONCE(!irq_fpu_usable());
>
> thing in kernel_fpu_begin() though, I guess it wouldn't hurt...
Hmm... note that we may call EFI runtime services from interrupt context
in efi_pstore_write(), so it seems like it would be possible to trigger
that WARN_ON_ONCE() there.
Seiji (Cc'd) might have some opinions on this.
Either way, if someone sends me a patch ontop of this one that swaps the
__kernel_fpu_begin() for kernel_fpu_begin() I can try them out in my
lab.
--
Matt Fleming, Intel Open Source Technology Center
next prev parent reply other threads:[~2014-04-25 11:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <tip-de05764e0b2a3d9559e099a2e134f8cef4500fdd@git.kernel.org>
2014-04-20 0:28 ` [tip:x86/efi] x86/efi: Save and restore FPU context around efi_calls (x86_64) Borislav Petkov
2014-04-25 11:09 ` Matt Fleming [this message]
2014-04-25 11:40 ` Borislav Petkov
2014-04-29 10:46 ` Matt Fleming
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