From: Matt Fleming <matt@codeblueprint.co.uk>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH] efi: runtime-wrappers: run UEFI Runtime Services with interrupts enabled
Date: Thu, 11 Feb 2016 16:04:05 +0000 [thread overview]
Message-ID: <20160211160405.GK4134@codeblueprint.co.uk> (raw)
In-Reply-To: <CALCETrWWLGjqXmPKs7wF3uJ+jR-xctU0eYOESdVxMm5b4w8JMw@mail.gmail.com>
On Mon, 08 Feb, at 11:37:58AM, Andy Lutomirski wrote:
> On Feb 4, 2016 5:58 AM, "Ard Biesheuvel" <ard.biesheuvel@linaro.org> wrote:
> >
> > OK, since Sai has confirmed that Windows leaves interrupts enabled when
> > calling the EFI variable store related runtime services, we should be able
> > to do the same for Linux, or at least be slightly more confident that we
> > won't have to back out this change later.
>
> Could this use a mutex instead of a spinlock?
>
> Can someone with a mixed mode setup read a variable in a loop and make
> sure it doesn't crash and burn? It should work fine, but explicit
> testing would be nice. (It's interesting mainly because doing a mixed
> mode call with interrupts on can result in a non-IST CPL0 to CPL0
> exception delivery, which won't result in a stack switch. This could
> easily trigger a stack overflow, logic bug, microcode bug, or
> as-yet-unknown CPU "feature".
I don't have physical hardware for testing mixed mode anymore (that
was returned to Intel when I left) but testing with Qemu didn't turn
up any problems when running with interrupts enabled.
> Hmm. We should also audit the mixed mode entry code to make sure that
> the high bits of RSP are explicitly clear before switching into compat
> mode. If I had to make a guess about how CPUs behave, I'd guess
> pessimistically: Intel CPUs clear the high bits of RSP when switching
> into long mode due to interrupt delivery, and AMD CPUs leave them set
> just to mess with us.
Interesting thought. I'm not aware of anyone testing mixed mode with
AMD CPUs, so that would be a good data point.
> Also, a WARN_ON(in_interrupt()) somewhere might be a good sanity check.
lockdep should catch this kind of stuff pretty quickly since we grab
the spinlock in every code path.
next prev parent reply other threads:[~2016-02-11 16:04 UTC|newest]
Thread overview: 54+ 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
2016-02-03 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
2016-02-03 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
2016-02-03 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 10:58 ` Ingo Molnar
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
2016-02-11 16:03 ` Matt Fleming
2016-02-11 16:04 ` Matt Fleming [this message]
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
2016-02-03 10:33 ` Ingo Molnar
2016-02-03 10:44 ` Matt Fleming
2016-02-03 10:50 ` Ingo Molnar
2016-02-03 11:18 ` Matt Fleming
2016-02-03 11:27 ` Ingo Molnar
2016-02-03 11:09 ` 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
2016-02-03 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)
2016-02-09 12:20 ` Ingo Molnar
2016-02-09 12:53 ` Laszlo Ersek
2016-02-09 13:14 ` Ingo Molnar
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