From: Peter Zijlstra <peterz@infradead.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-crypto@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Dave Martin <dave.martin@arm.com>,
Mark Brown <broonie@kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
Eric Biggers <ebiggers@kernel.org>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Ingo Molnar <mingo@kernel.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?
next prev parent reply other threads:[~2021-02-16 10:11 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
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