From: "Björn Töpel" <bjorn@kernel.org>
To: Andy Chiu <andy.chiu@sifive.com>,
linux-riscv@lists.infradead.org, palmer@dabbelt.com
Cc: vineetg@rivosinc.com, 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>,
"Guo Ren" <guoren@kernel.org>,
"Conor Dooley" <conor.dooley@microchip.com>,
"Yipeng Zou" <zouyipeng@huawei.com>,
"Jisheng Zhang" <jszhang@kernel.org>,
"Vincent Chen" <vincent.chen@sifive.com>,
"Heiko Stuebner" <heiko@sntech.de>,
"Björn Töpel" <bjorn@rivosinc.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Mathis Salmen" <mathis.salmen@matsal.de>,
"Andrew Bresticker" <abrestic@rivosinc.com>
Subject: Re: [v2, 1/5] riscv: sched: defer restoring Vector context for user
Date: Tue, 15 Aug 2023 12:41:33 +0200 [thread overview]
Message-ID: <87o7j8egf6.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <20230721112855.1006-2-andy.chiu@sifive.com>
Andy Chiu <andy.chiu@sifive.com> writes:
> User will use its Vector registers only after the kernel really returns
> to the userspace. So we can delay restoring Vector registers as long as
> we are still running in kernel mode. So, add a thread flag to indicates
> the need of restoring Vector and do the restore at the last
> arch-specific exit-to-user hook. This save the context restoring cost
> when we switch over multiple processes that run V in kernel mode. For
> example, if the kernel performs a context swicth from A->B->C, and
> returns to C's userspace, then there is no need to restore B's
> V-register.
>
> Besides, this also prevents us from repeatedly restoring V context when
> executing kernel-mode Vector multiple times for the upcoming kenel-mode
> Vector patches.
>
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
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next prev parent reply other threads:[~2023-08-15 10:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-21 11:28 [v2, 0/5] riscv: support kernel-mode Vector Andy Chiu
2023-07-21 11:28 ` [v2, 1/5] riscv: sched: defer restoring Vector context for user Andy Chiu
2023-08-15 10:41 ` Björn Töpel [this message]
2023-07-21 11:28 ` [v2, 2/5] riscv: Add support for kernel mode vector Andy Chiu
2023-07-24 10:48 ` Conor Dooley
2023-07-24 15:48 ` Andy Chiu
2023-08-15 11:28 ` Björn Töpel
2023-08-16 23:36 ` Guo Ren
2023-07-21 11:28 ` [v2, 3/5] riscv: Add vector extension XOR implementation Andy Chiu
2023-07-24 10:51 ` Conor Dooley
2023-07-21 11:28 ` [v2, 4/5] riscv: vector: do not pass task_struct into riscv_v_vstate_{save,restore}() Andy Chiu
2023-07-21 11:28 ` [v2, 5/5] riscv: vector: allow kernel-mode Vector with preemption Andy Chiu
2023-07-24 12:18 ` Conor Dooley
2023-07-24 15:45 ` Andy Chiu
2023-07-24 16:26 ` Conor Dooley
2023-08-15 12:19 ` Björn Töpel
2023-08-16 23:18 ` [v2, 0/5] riscv: support kernel-mode Vector Guo Ren
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