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From: Ingo Molnar <mingo@kernel.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>,
	"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>
Subject: Re: [PATCH 07/14] efi: runtime-wrappers: Run UEFI Runtime Services with interrupts enabled
Date: Wed, 3 Feb 2016 11:58:51 +0100	[thread overview]
Message-ID: <20160203105851.GA22159@gmail.com> (raw)
In-Reply-To: <CAKv+Gu-AWTQNG3ObSZt0cHV1YFb8UbYpkq-uVBqMW0wryfv_ig@mail.gmail.com>


* 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.

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.

Thanks,

	Ingo

  reply	other threads:[~2016-02-03 10:58 UTC|newest]

Thread overview: 67+ 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
2016-02-03 11:31   ` [tip:efi/core] " tip-bot for Ard Biesheuvel
2016-02-01 22:06 ` [PATCH 02/14] efi: Remove redundant efi_set_variable_nonblocking prototype Matt Fleming
2016-02-01 22:06   ` Matt Fleming
2016-02-03 11:31   ` [tip:efi/core] efi: Remove redundant efi_set_variable_nonblocking () prototype tip-bot for Ard Biesheuvel
2016-02-01 22:06 ` [PATCH 03/14] efi: runtime-wrappers: Add a nonblocking version of QueryVariableInfo Matt Fleming
2016-02-01 22:06   ` Matt Fleming
2016-02-03 11:31   ` [tip:efi/core] efi/runtime-wrappers: Add a nonblocking version of QueryVariableInfo() tip-bot for Ard Biesheuvel
2016-02-01 22:06 ` [PATCH 04/14] efi: Add nonblocking option to efi_query_variable_store() Matt Fleming
2016-02-03 11:32   ` [tip:efi/core] " tip-bot for Ard Biesheuvel
2016-02-01 22:06 ` [PATCH 05/14] efi: runtime-wrappers: Remove out of date comment regarding in_nmi() Matt Fleming
2016-02-03 11:32   ` [tip:efi/core] efi/runtime-wrappers: " tip-bot for Ard Biesheuvel
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   ` Matt Fleming
2016-02-03 11:32   ` [tip:efi/core] efi: Runtime-wrapper: " tip-bot for Ard Biesheuvel
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
2016-02-03  9:57     ` Ard Biesheuvel
2016-02-03  9:57       ` Ard Biesheuvel
2016-02-03 10:58       ` Ingo Molnar [this message]
2016-02-03 11:33         ` Ard Biesheuvel
2016-02-03 12:01           ` Matt Fleming
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
2016-02-09 16:52             ` Ard Biesheuvel
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
2016-02-03 11:33   ` [tip:efi/core] " tip-bot for Geliang Tang
2016-02-01 22:07 ` [PATCH 09/14] x86/efi-bgrt: Don't ignore the BGRT if the 'valid' bit is 0 Matt Fleming
2016-02-03 11:33   ` [tip:efi/core] x86/efi/bgrt: " tip-bot for Môshe van der Sterre
2016-02-01 22:07 ` [PATCH 10/14] efi: Make checkpatch complain less about efi.h GUID additions Matt Fleming
2016-02-01 22:07   ` Matt Fleming
2016-02-03 10:33   ` Ingo Molnar
2016-02-03 10:33     ` Ingo Molnar
2016-02-03 10:44     ` Matt Fleming
2016-02-03 10:50       ` Ingo Molnar
2016-02-03 10:50         ` Ingo Molnar
2016-02-03 11:18         ` Matt Fleming
2016-02-03 11:27           ` Ingo Molnar
2016-02-03 11:27             ` Ingo Molnar
2016-02-03 11:09     ` Joe Perches
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
2016-02-03 11:33   ` [tip:efi/core] " tip-bot for Robert Elliott
2016-02-01 22:07 ` [PATCH 12/14] efi: Add NV memory attribute Matt Fleming
2016-02-02  8:54   ` Laszlo Ersek
2016-02-02  8:54     ` Laszlo Ersek
2016-02-03 11:34   ` [tip:efi/core] " tip-bot for Robert Elliott
2016-02-01 22:07 ` [PATCH 13/14] efi: Add Persistent Memory type name Matt Fleming
2016-02-02  8:56   ` Laszlo Ersek
2016-02-03 11:34   ` [tip:efi/core] " tip-bot for Robert Elliott
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
2016-02-03 15:25         ` Elliott, Robert (Persistent Memory)
2016-02-03 15:25           ` Elliott, Robert (Persistent Memory)
2016-02-09 12:20           ` Ingo Molnar
2016-02-09 12:53             ` Laszlo Ersek
2016-02-09 12:53               ` Laszlo Ersek
2016-02-09 13:14               ` Ingo Molnar
2016-02-09 13:14                 ` Ingo Molnar

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