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From: Heiko Stuebner <heiko@sntech.de>
To: linux-riscv@lists.infradead.org, palmer@dabbelt.com
Cc: vineetg@rivosinc.com, bjorn@kernel.org, greentime.hu@sifive.com,
	paul.walmsley@sifive.com, guoren@linux.alibaba.com,
	anup@brainfault.org, atishp@atishpatra.org,
	heiko.stuebner@vrull.eu, Andy Chiu <andy.chiu@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Andy Chiu <andy.chiu@sifive.com>
Subject: Re: [v1, 0/6] riscv: support kernel-mode Vector
Date: Sun, 16 Jul 2023 11:26:03 +0200	[thread overview]
Message-ID: <4216859.NG923GbCHz@phil> (raw)
In-Reply-To: <20230715150032.6917-1-andy.chiu@sifive.com>

Am Samstag, 15. Juli 2023, 17:00:26 CEST schrieb Andy Chiu:
> This series provides support for running Vector code in kernel mode. The
> implementation is based on the v12 series of the Vector series, but with
> some additions. First, we introduce a mechanism to defer restoring
> Vector context for userspace programs (patch 1). This is similar to
> arm64 and x86's approaches when dealing with extra userspace register
> context. And it is benefitial to both Vector in user and kernel-mode.
> Then, patch 2, 3 add the kernel-mode Vector patch from v12 with minor
> modifications. At the end of the series, patch 4, 5, 6 add supports for
> making kernel-mode Vector code preemptible. We do this by adding
> kernel-mode Vector context, and keeping track of the frame where V
> context is last valid. We believe that enabling preemption of running V
> is a critical path for getting V more generally available in the
> kernel-mode. Besides, with status.VS, we can easily tell if
> saving/restoring V is required. This reduce the level of cost when
> running SIMD in kernel mode as compared to other arches. Other arches
> usually do not have a way to tell if extra context is dirty. Thus, if
> they also want to support running preemptible code with extra registers,
> then they must save/restore extra context at each context switch even if
> registers are not dirty.
> 
> The series is tested by loading a kernel module on a preemptive kernel.
> The module launches multiple kworkers which run Vector operations and
> verifies with scalar code. Also, the module provides userspace intefaces
> via fops to verify if we can run Vector code on syscall path.
> 
> Changes from the vector v12 series (for patch 2, 3):
>  - return a failure code when kernel_rvv_begin() fails.
>  - Do not immediately restore user's V context.

This works nicely with my vector crypto patchset rebased on
top of it:

Tested-by: Heiko Stuebner <heiko@sntech.de>



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      parent reply	other threads:[~2023-07-16  9:26 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-15 15:00 [v1, 0/6] riscv: support kernel-mode Vector Andy Chiu
2023-07-15 15:00 ` [v1, 1/6] riscv: sched: defer restoring Vector context for user Andy Chiu
2023-07-17  9:46   ` Conor Dooley
2023-07-17 16:03     ` Andy Chiu
2023-07-15 15:00 ` [v1, 2/6] riscv: Add support for kernel mode vector Andy Chiu
2023-07-17 10:22   ` Conor Dooley
2023-07-20 14:54     ` Andy Chiu
2023-07-15 15:00 ` [v1, 3/6] riscv: Add vector extension XOR implementation Andy Chiu
2023-07-17 10:25   ` Conor Dooley
2023-07-20 14:56     ` Andy Chiu
2023-07-15 15:00 ` [v1, 4/6] riscv: vector: do not pass task_struct into riscv_v_vstate_{save,restore}() Andy Chiu
2023-07-17 10:32   ` Conor Dooley
2023-07-20 14:59     ` Andy Chiu
2023-07-15 15:00 ` [v1, 5/6] riscv: vector: allow kernel-mode Vector with preemption Andy Chiu
2023-07-17 11:05   ` Conor Dooley
2023-07-20 15:13     ` Andy Chiu
2023-07-15 15:00 ` [v1, 6/6] riscv: vector: enable preemptive kernel-mode Vector to be built Andy Chiu
2023-07-17 11:11   ` Conor Dooley
2023-07-16  9:26 ` Heiko Stuebner [this message]

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