From: Matt Fleming <matt@codeblueprint.co.uk>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Subject: Re: [PATCH 07/14] efi: runtime-wrappers: Run UEFI Runtime Services with interrupts enabled
Date: Wed, 3 Feb 2016 12:01:37 +0000 [thread overview]
Message-ID: <20160203120137.GE2597@codeblueprint.co.uk> (raw)
In-Reply-To: <CAKv+Gu8KZW4m1O5KheBpteOr6tCgNT-FnVkXK-g05=qrzT5xiA@mail.gmail.com>
On Wed, 03 Feb, at 12:33:10PM, Ard Biesheuvel wrote:
> On 3 February 2016 at 11:58, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> >
> >> > More fundamentally, this makes me nervous:
> >> >
> >> > > The UEFI spec allows Runtime Services to be invoked with interrupts
> >> > > enabled. [...]
> >> >
> >> > So what really matters is not what the spec says, but how Windows executes
> >> > UEFI firmware code in practice.
> >> >
> >> > If major versions of Windows calls UEFI firmware with interrupts disabled,
> >> > then frankly I don't think we should interrupt them under Linux either,
> >> > regardless of what the spec says ...
> >> >
> >> > Random firmware code getting interrupted by the OS changes timings and might
> >> > have other side effects the firmware code might not expect - so the question
> >> > is, does Windows already de facto allow the IRQ preemption of firmware calls?
> >> >
> >>
> >> Good question. I will try to find out.
> >
> > Note that if there's a reasonable (but not 100%) case in favor of keeping irqs
> > enabled, we can try your patch, with the possibility that we might have to revert
> > it, should it cause problems.
> >
>
> I think this might have been the reason Matt wanted this in -next
> early, but I will let him confirm whether that was the case.
It was indeed. Additionally I didn't want the EFI material to miss the
merge window again.
> > In practice we probably already interrupt EFI services with NMI interrupts, which
> > can be pretty heavy as well if they for example generate printks.
> >
> > So I'm not against this change in a strong fashion - I'm just a bit cautious and
> > it would be nice to know how Windows behaves here.
> >
>
> I am not sure how yet, but I am going to try and figure out what
> Windows does. I suppose hacking OVMF to record some IRQ mask
> information when RT services are being invoked should be sufficient,
> but I am going to need some help from someone that understands OVMF
> and x86 (Matt?)
Sure, I can help out with that. Hit me up on IRC. I'm also looping in
Sai who has done OVMF hacking for OS diagnostics in the past.
next prev parent reply other threads:[~2016-02-03 12:01 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-01 22:06 [GIT PULL 00/14] EFI changes for v4.6 Matt Fleming
2016-02-01 22:06 ` [PATCH 01/14] efi: Expose non-blocking set_variable() wrapper to efivars Matt Fleming
[not found] ` <1454364428-494-1-git-send-email-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-02-01 22:06 ` [PATCH 02/14] efi: Remove redundant efi_set_variable_nonblocking prototype Matt Fleming
2016-02-01 22:06 ` [PATCH 03/14] efi: runtime-wrappers: Add a nonblocking version of QueryVariableInfo Matt Fleming
2016-02-01 22:07 ` [PATCH 06/14] efi: runtime-wrapper: Get rid of the rtc_lock spinlock Matt Fleming
2016-02-01 22:07 ` [PATCH 10/14] efi: Make checkpatch complain less about efi.h GUID additions Matt Fleming
[not found] ` <1454364428-494-11-git-send-email-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-02-03 10:33 ` Ingo Molnar
2016-02-03 10:44 ` Matt Fleming
[not found] ` <20160203104432.GA2597-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-02-03 10:50 ` Ingo Molnar
2016-02-03 11:18 ` Matt Fleming
[not found] ` <20160203111838.GB2597-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-02-03 11:27 ` Ingo Molnar
2016-02-03 11:09 ` Joe Perches
2016-02-01 22:06 ` [PATCH 04/14] efi: Add nonblocking option to efi_query_variable_store() Matt Fleming
2016-02-01 22:06 ` [PATCH 05/14] efi: runtime-wrappers: Remove out of date comment regarding in_nmi() Matt Fleming
2016-02-01 22:07 ` [PATCH 07/14] efi: runtime-wrappers: Run UEFI Runtime Services with interrupts enabled Matt Fleming
2016-02-03 9:43 ` Ingo Molnar
[not found] ` <20160203094340.GA15890-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-02-03 9:57 ` Ard Biesheuvel
2016-02-03 10:58 ` Ingo Molnar
2016-02-03 11:33 ` Ard Biesheuvel
2016-02-03 12:01 ` Matt Fleming [this message]
2016-02-04 13:58 ` [PATCH] efi: runtime-wrappers: run " Ard Biesheuvel
2016-02-08 15:16 ` Matt Fleming
2016-02-08 19:37 ` Andy Lutomirski
[not found] ` <CALCETrWWLGjqXmPKs7wF3uJ+jR-xctU0eYOESdVxMm5b4w8JMw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-02-09 16:52 ` Ard Biesheuvel
2016-02-11 16:03 ` Matt Fleming
2016-02-11 16:04 ` Matt Fleming
2016-02-01 22:07 ` [PATCH 08/14] efivars: Use to_efivar_entry Matt Fleming
2016-02-01 22:07 ` [PATCH 09/14] x86/efi-bgrt: Don't ignore the BGRT if the 'valid' bit is 0 Matt Fleming
2016-02-01 22:07 ` [PATCH 11/14] x86/efi: Show actual ending addresses in efi_print_memmap Matt Fleming
2016-02-02 8:49 ` Laszlo Ersek
2016-02-01 22:07 ` [PATCH 12/14] efi: Add NV memory attribute Matt Fleming
[not found] ` <1454364428-494-13-git-send-email-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-02-02 8:54 ` Laszlo Ersek
2016-02-01 22:07 ` [PATCH 13/14] efi: Add Persistent Memory type name Matt Fleming
2016-02-02 8:56 ` Laszlo Ersek
2016-02-01 22:07 ` [PATCH 14/14] x86/efi: Print size in binary units in efi_print_memmap Matt Fleming
2016-02-02 9:22 ` Laszlo Ersek
2016-02-03 10:40 ` Ingo Molnar
2016-02-03 11:28 ` Matt Fleming
2016-02-03 12:36 ` Andy Shevchenko
[not found] ` <20160203112829.GC2597-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-02-03 15:25 ` Elliott, Robert (Persistent Memory)
2016-02-09 12:20 ` Ingo Molnar
[not found] ` <20160209122018.GA4178-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-02-09 12:53 ` Laszlo Ersek
[not found] ` <56B9E166.6030405-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-02-09 13:14 ` Ingo Molnar
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