From: Florian Weimer <fweimer@redhat.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: Yao Qi <qiyaoltc@gmail.com>,
libc-alpha@sourceware.org,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Marc Zyngier <Marc.Zyngier@arm.com>,
gdb@sourceware.org,
Christoffer Dall <christoffer.dall@linaro.org>,
Alan Hayward <alan.hayward@arm.com>,
Torvald Riegel <triegel@redhat.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 00/29] arm64: Scalable Vector Extension core support
Date: Thu, 01 Dec 2016 09:21:00 -0000 [thread overview]
Message-ID: <dbcd545f-1358-6a80-5a9f-3e4a3c93189a@redhat.com> (raw)
In-Reply-To: <20161130135631.GK1574@e103592.cambridge.arm.com>
On 11/30/2016 02:56 PM, Dave Martin wrote:
> If we do have distinct "set process VL" and "set thread VL" interfaces,
> then my view is that the former should fail if there are already
> multiple threads, rather than just setting the VL of a single thread or
> (worse) asynchronously changing the VL of threads other than the
> caller...
Yes, looks feasible to me.
>>> I'm not familiar with resumable functions/executors -- are these in
>>> the C++ standards yet (not that that would cause me to be familiar
>>> with them... ;) Any implementation of coroutines (i.e.,
>>> cooperative switching) is likely to fall under the "setcontext"
>>> argument above.
>>
>> There are different ways to implement coroutines. Stack switching (like
>> setcontext) is obviously impacted by non-uniform register sizes. But even
>> the most conservative variant, rather similar to switch-based emulation you
>> sometimes see in C coroutine implementations, might have trouble restoring
>> the state if it just cannot restore the saved state due to register size
>> reductions.
>
> Which is not a problem if the variably-sized state is not part of the
> switched context?
The VL value is implicitly thread-local data, and the encoded state may
have an implicit dependency on it, although it does not contain vector
registers as such.
> Because the SVE procedure call standard determines that the SVE
> registers are caller-save,
By the way, how is this implemented? Some of them overlap existing
callee-saved registers.
> they are not live at any external function
> boundary -- so in cooperative switching it is useless to save/restore
> this state unless the coroutine framework is defined to have a special
> procedure call standard.
It can use the standard calling convention, but it may have selected a
particular implementation based on the VL value before suspension.
Florian
next prev parent reply other threads:[~2016-12-01 9:21 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 03/29] arm64: signal: factor out signal frame record allocation 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 19:40 ` [RFC PATCH 04/29] arm64: signal: Allocate extra sigcontext space as needed Dave Martin
2016-11-25 19:40 ` [RFC PATCH 05/29] arm64: signal: Parse extra_context during sigreturn 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 16/29] arm64/sve: signal: Add SVE state record to sigcontext 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 17/29] arm64/sve: signal: Dump Scalable Vector Extension registers to user stack 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 [this message]
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
2016-11-30 14:06 ` Dave Martin
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