From: Andy Lutomirski <luto@amacapital.net>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>,
"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: Mon, 8 Feb 2016 11:37:58 -0800 [thread overview]
Message-ID: <CALCETrWWLGjqXmPKs7wF3uJ+jR-xctU0eYOESdVxMm5b4w8JMw@mail.gmail.com> (raw)
In-Reply-To: <1454594327-5444-1-git-send-email-ard.biesheuvel@linaro.org>
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".
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.
Also, a WARN_ON(in_interrupt()) somewhere might be a good sanity check.
--Andy
next prev parent reply other threads:[~2016-02-08 19:38 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 [this message]
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
2016-02-03 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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