From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Florian Weimer <fweimer@redhat.com>,
Dave Martin <Dave.Martin@arm.com>,
<linux-arm-kernel@lists.infradead.org>
Cc: <nd@arm.com>, Christoffer Dall <christoffer.dall@linaro.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Marc Zyngier <Marc.Zyngier@arm.com>,
Alan Hayward <alan.hayward@arm.com>, <libc-alpha@sourceware.org>,
<gdb@sourceware.org>, Torvald Riegel <triegel@redhat.com>
Subject: Re: [RFC PATCH 00/29] arm64: Scalable Vector Extension core support
Date: Wed, 30 Nov 2016 11:06:00 -0000 [thread overview]
Message-ID: <583EB285.5050305@arm.com> (raw)
In-Reply-To: <7a35d1ae-73df-03a5-c9d6-1a52754acf25@redhat.com>
On 30/11/16 10:08, Florian Weimer wrote:
> On 11/25/2016 08:38 PM, Dave Martin wrote:
>> The Scalable Vector Extension (SVE) [1] is an extension to AArch64 which
>> adds extra SIMD functionality and supports much larger vectors.
>>
>> This series implements core Linux support for SVE.
>>
>> Recipents not copied on the whole series can find the rest of the
>> patches in the linux-arm-kernel archives [2].
>>
>>
>> The first 5 patches "arm64: signal: ..." factor out the allocation and
>> placement of state information in the signal frame. The first three
>> are prerequisites for the SVE support patches.
>>
>> Patches 04-05 implement expansion of the signal frame, and may remain
>> controversial due to ABI break issues:
>>
>> * Discussion is needed on how userspace should detect/negotiate signal
>> frame size in order for this expansion mechanism to be workable.
>
> I'm leaning towards a simple increase in the glibc headers (despite the ABI risk), plus a personality flag to
> disable really wide vector registers in case this causes problems with old binaries.
>
if the kernel does not increase the size and libc
does not add size checks then old binaries would
work with new libc just fine..
but that's non-conforming, posix requires the check.
if the kernel increases the size then it has to be
changed in bionic and musl as well and old binaries
may break.
> A more elaborate mechanism will likely introduce more bugs than it makes existing applications working, due to
> its complexity.
>
>> The remaining patches implement initial SVE support for Linux, with the
>> following limitations:
>>
>> * No KVM/virtualisation support for guests.
>>
>> * No independent SVE vector length configuration per thread. This is
>> planned, but will follow as a separate add-on series.
>
> Per-thread register widths will likely make coroutine switching (setcontext) and C++ resumable
> functions/executors quite challenging.
>
i'd assume it's undefined to context switch to a different
thread or to resume a function on a different thread
(because the implementation can cache thread local state
on the stack: e.g. errno pointer).. of course this does
not stop ppl from doing it, but the practice is questionable.
> Can you detail your plans in this area?
>
> Thanks,
> Florian
next prev parent reply other threads:[~2016-11-30 11:06 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-25 19:39 Dave Martin
2016-11-25 19:39 ` [RFC PATCH 01/29] arm64: signal: Refactor sigcontext parsing in rt_sigreturn Dave Martin
2016-11-25 19:39 ` [RFC PATCH 02/29] arm64: signal: factor frame layout and population into separate passes Dave Martin
2016-11-25 19:39 ` [RFC PATCH 03/29] arm64: signal: factor out signal frame record allocation Dave Martin
2016-11-25 19:40 ` [RFC PATCH 05/29] arm64: signal: Parse extra_context during sigreturn Dave Martin
2016-11-25 19:40 ` [RFC PATCH 04/29] arm64: signal: Allocate extra sigcontext space as needed Dave Martin
2016-11-25 19:41 ` [RFC PATCH 17/29] arm64/sve: signal: Dump Scalable Vector Extension registers to user stack Dave Martin
2016-11-25 19:41 ` [RFC PATCH 24/29] arm64/sve: Discard SVE state on system call Dave Martin
2016-11-25 19:41 ` [RFC PATCH 18/29] arm64/sve: signal: Restore FPSIMD/SVE state in rt_sigreturn Dave Martin
2016-11-25 19:41 ` [RFC PATCH 16/29] arm64/sve: signal: Add SVE state record to sigcontext Dave Martin
2016-11-30 9:56 ` [RFC PATCH 00/29] arm64: Scalable Vector Extension core support Yao Qi
2016-11-30 12:07 ` Dave Martin
2016-11-30 12:22 ` Szabolcs Nagy
2016-11-30 14:10 ` Dave Martin
2016-11-30 12:38 ` Florian Weimer
2016-11-30 13:56 ` Dave Martin
2016-12-01 9:21 ` Florian Weimer
2016-12-01 10:30 ` Dave Martin
2016-12-01 12:19 ` Dave Martin
2016-12-05 10:44 ` Florian Weimer
2016-12-05 11:07 ` Szabolcs Nagy
2016-12-05 15:05 ` Dave Martin
2016-12-02 11:49 ` Dave Martin
2016-12-02 16:34 ` Florian Weimer
2016-12-02 16:59 ` Joseph Myers
2016-12-02 18:21 ` Dave Martin
2016-12-02 21:57 ` Joseph Myers
2016-12-02 21:56 ` Yao Qi
2016-12-05 15:12 ` Dave Martin
2016-12-05 22:42 ` Torvald Riegel
2016-12-06 14:46 ` Dave Martin
2016-11-30 10:08 ` Florian Weimer
2016-11-30 11:06 ` Szabolcs Nagy [this message]
2016-11-30 14:06 ` Dave Martin
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