From: Peter Zijlstra <peterz@infradead.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
Catalin Marinas <catalin.marinas@arm.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Eric Biggers <ebiggers@kernel.org>,
Mark Brown <broonie@kernel.org>,
linux-crypto@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>, Dave Martin <dave.martin@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 0/5] running kernel mode SIMD with softirqs disabled
Date: Tue, 16 Feb 2021 11:09:05 +0100 [thread overview]
Message-ID: <YCuZwWWGtqf8PaAf@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201218170106.23280-1-ardb@kernel.org>
On Fri, Dec 18, 2020 at 06:01:01PM +0100, Ard Biesheuvel wrote:
> [ TL;DR for the non-ARM folks on CC: disabling softirq processing when using
> SIMD in kernel mode could reduce complexity and improve performance, but we
> need to decide whether we can do this, and how much softirq processing
> latency we can tolerate. If we can find a satisfactory solution for this,
> we might do the same for x86 and 32-bit ARM as well. ]
> - could we do the same on x86, now that kernel_fpu_begin/end is no longer
> expensive?
Can't we simply save/restore the relevant register set?
So something like (note amluto was wanting to add a regset argument):
<task>
kernel_fpu_begin(MMX)
<SIRQ>
kernel_fpu_begin(SSE)
kernel_fpu_end();
</SIRQ>
...
kernel_fpu_end()
Would have to save the MMX regs on first SIRQ invocation of
kernel_fpu_begin(), and then have softirq context termination </SIRQ>
above, restore it.
I mean, we already do much the same for the first kernel_fpu_begin(),
that has to save the user registers, which will be restore when we go
back to userspace.
So why not do exactly the same for softirq context?
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-02-16 10:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 17:01 [RFC PATCH 0/5] running kernel mode SIMD with softirqs disabled Ard Biesheuvel
2020-12-18 17:01 ` [RFC PATCH 1/5] crypto: aead - disallow en/decrypt for non-task or non-softirq context Ard Biesheuvel
2020-12-18 17:01 ` [RFC PATCH 2/5] crypto: skcipher " Ard Biesheuvel
2020-12-18 17:01 ` [RFC PATCH 3/5] crypto: arm64/gcm-aes-ce - add NEON yield support Ard Biesheuvel
2020-12-18 17:01 ` [RFC PATCH 4/5] arm64: fpsimd: run kernel mode NEON with softirqs disabled Ard Biesheuvel
2021-01-19 16:00 ` Dave Martin
2021-01-19 16:29 ` Ard Biesheuvel
2021-01-20 15:44 ` Dave Martin
2021-02-15 18:30 ` Ard Biesheuvel
2020-12-18 17:01 ` [RFC PATCH 5/5] crypto: arm64/gcm-aes-ce - remove non-SIMD fallback path Ard Biesheuvel
2020-12-19 2:04 ` [RFC PATCH 0/5] running kernel mode SIMD with softirqs disabled Herbert Xu
2021-01-14 8:22 ` Ard Biesheuvel
2021-02-16 10:09 ` Peter Zijlstra [this message]
2021-02-16 10:35 ` Ard Biesheuvel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YCuZwWWGtqf8PaAf@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=ardb@kernel.org \
--cc=bigeasy@linutronix.de \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=dave.martin@arm.com \
--cc=ebiggers@kernel.org \
--cc=herbert@gondor.apana.org.au \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).