From: Will Deacon <will@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>, linux-crypto@vger.kernel.org
Cc: catalin.marinas@arm.com, kernel-team@android.com,
mark.rutland@arm.com, Dave Martin <dave.martin@arm.com>,
Eric Biggers <ebiggers@google.com>,
herbert@gondor.apana.org.au,
linux-arm-kernel@lists.infradead.org
Subject: Re: (subset) Re: [PATCH v2 0/9] arm64: rework NEON yielding to avoid scheduling from asm code
Date: Thu, 4 Feb 2021 10:33:48 +0000 [thread overview]
Message-ID: <20210204103347.GA20410@willie-the-truck> (raw)
In-Reply-To: <161238528350.1984862.12324465919265084208.b4-ty@kernel.org>
On Wed, Feb 03, 2021 at 09:31:31PM +0000, Will Deacon wrote:
> On Wed, 3 Feb 2021 12:36:17 +0100, Ard Biesheuvel wrote:
> > Given how kernel mode NEON code disables preemption (to ensure that the
> > FP/SIMD register state is protected without having to context switch it),
> > we need to take care not to let those algorithms operate on unbounded
> > input data, or we may end up with excessive scheduling blackouts on
> > CONFIG_PREEMPT kernels.
> >
> > This is currently handled by the cond_yield_neon macros, which check the
> > preempt count and the TIF_NEED_RESCHED flag from assembler code, and call
> > into kernel_neon_end()+kernel_neon_begin(), triggering a reschedule.
> > This works as expected, but is a bit messy, given how much of the state
> > preserve/restore code in the algorithm needs to be duplicated, as well as
> > causing the need to manage the stack frame explicitly. All of this is better
> > handled by the compiler, especially now that we have enabled features such
> > as the shadow call stack and BTI, and are working to improve call stack
> > validation.
> >
> > [...]
>
> Applied first patch only to arm64 (for-next/crypto), thanks!
Oops, looks like I typo'd the external branch (for-next/crypo). No offense
intended! I'll rename it now; SHAs will stay the same.
Will
next prev parent reply other threads:[~2021-02-04 10:36 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 11:36 [PATCH v2 0/9] arm64: rework NEON yielding to avoid scheduling from asm code Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 1/9] arm64: assembler: add cond_yield macro Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 2/9] crypto: arm64/sha1-ce - simplify NEON yield Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 3/9] crypto: arm64/sha2-ce " Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 4/9] crypto: arm64/sha3-ce " Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 5/9] crypto: arm64/sha512-ce " Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 6/9] crypto: arm64/aes-neonbs - remove NEON yield calls Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 7/9] crypto: arm64/aes-ce-mac - simplify NEON yield Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 8/9] crypto: arm64/crc-t10dif - move NEON yield to C code Ard Biesheuvel
2021-02-03 11:36 ` [PATCH v2 9/9] arm64: assembler: remove conditional NEON yield macros Ard Biesheuvel
2021-02-03 21:31 ` (subset) Re: [PATCH v2 0/9] arm64: rework NEON yielding to avoid scheduling from asm code Will Deacon
2021-02-04 2:44 ` Herbert Xu
2021-02-04 8:29 ` Ard Biesheuvel
2021-02-04 11:10 ` Herbert Xu
2021-02-04 13:03 ` Will Deacon
2021-02-04 19:45 ` Herbert Xu
2021-02-04 10:33 ` Will Deacon [this message]
2021-02-10 7:23 ` Herbert Xu
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