From: Matt Fleming <matt-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>
To: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Cc: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
"Luck, Tony" <tony.luck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [GIT PULL] EFI changes for v3.16
Date: Tue, 20 May 2014 21:27:55 +0100 [thread overview]
Message-ID: <20140520202755.GI4798@console-pimps.org> (raw)
In-Reply-To: <537A8A03.8060604-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
On Mon, 19 May, at 03:47:31PM, H. Peter Anvin wrote:
>
> How on earth does this solve anything? The only thing we add here is a
> WARN_ON_ONCE()... but the above text already tells us we have a problem.
>
> It seems, rather, that we need to figure out how to deal with a pstore
> in this case. There are a few possibilities:
>
> 1. We could keep an XSAVE buffer area around for this particular use.
> I am *assuming* we don't let more than one CPU into EFI, because I
> cannot for my life imagine that this is safe in typical CPUs.
Correct. This is actually prohibited by the spec, so we have a lock to
enforce it.
> 2. Drop the pstore on the floor if !irq_fpu_usable().
>
> 3. Allow the pstore, then die (on the assumption that we're dead
> anyway.)
Personally, I'd prefer 2, but I'm open to suggestions.
--
Matt Fleming, Intel Open Source Technology Center
WARNING: multiple messages have this Message-ID (diff)
From: Matt Fleming <matt@console-pimps.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
Borislav Petkov <bp@alien8.de>,
"Luck, Tony" <tony.luck@intel.com>
Subject: Re: [GIT PULL] EFI changes for v3.16
Date: Tue, 20 May 2014 21:27:55 +0100 [thread overview]
Message-ID: <20140520202755.GI4798@console-pimps.org> (raw)
In-Reply-To: <537A8A03.8060604@zytor.com>
On Mon, 19 May, at 03:47:31PM, H. Peter Anvin wrote:
>
> How on earth does this solve anything? The only thing we add here is a
> WARN_ON_ONCE()... but the above text already tells us we have a problem.
>
> It seems, rather, that we need to figure out how to deal with a pstore
> in this case. There are a few possibilities:
>
> 1. We could keep an XSAVE buffer area around for this particular use.
> I am *assuming* we don't let more than one CPU into EFI, because I
> cannot for my life imagine that this is safe in typical CPUs.
Correct. This is actually prohibited by the spec, so we have a lock to
enforce it.
> 2. Drop the pstore on the floor if !irq_fpu_usable().
>
> 3. Allow the pstore, then die (on the assumption that we're dead
> anyway.)
Personally, I'd prefer 2, but I'm open to suggestions.
--
Matt Fleming, Intel Open Source Technology Center
next prev parent reply other threads:[~2014-05-20 20:27 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-03 13:04 [GIT PULL] EFI changes for v3.16 Matt Fleming
2014-05-03 13:04 ` Matt Fleming
[not found] ` <20140503130447.GW26088-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>
2014-05-19 10:51 ` Matt Fleming
2014-05-19 10:51 ` Matt Fleming
[not found] ` <20140519105129.GF4798-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>
2014-05-19 22:47 ` H. Peter Anvin
2014-05-19 22:47 ` H. Peter Anvin
[not found] ` <537A8A03.8060604-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2014-05-19 23:10 ` Borislav Petkov
2014-05-19 23:10 ` Borislav Petkov
2014-05-20 0:17 ` H. Peter Anvin
2014-05-20 11:00 ` Borislav Petkov
2014-05-20 20:27 ` Matt Fleming [this message]
2014-05-20 20:27 ` Matt Fleming
-- strict thread matches above, loose matches on Subject: below --
2014-04-19 10:06 Matt Fleming
2014-04-19 10:06 ` Matt Fleming
[not found] ` <20140419100653.GA26088-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>
2014-04-19 22:42 ` H. Peter Anvin
2014-04-19 22:42 ` H. Peter Anvin
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