linux-kernel - Re: [PATCH] riscv: Discard vector state on syscalls

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Message-ID: <874jmuns3y.fsf@all.your.base.are.belong.to.us>
Date:   Mon, 26 Jun 2023 17:46:57 +0200
From:   Björn Töpel <bjorn@...nel.org>
To:     Vineet Gupta <vineetg@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org
Cc:     Björn Töpel <bjorn@...osinc.com>,
        linux-kernel@...r.kernel.org, linux@...osinc.com,
        Palmer Dabbelt <palmer@...osinc.com>,
        Rémi Denis-Courmont 
        <remi@...lab.net>, Darius Rad <darius@...espec.com>,
        Andy Chiu <andy.chiu@...ive.com>
Subject: Re: [PATCH] riscv: Discard vector state on syscalls

Vineet Gupta <vineetg@...osinc.com> writes:

> On 6/22/23 10:36, Björn Töpel wrote:
>> From: Björn Töpel <bjorn@...osinc.com>
>>
>> The RISC-V vector specification states:
>>    Executing a system call causes all caller-saved vector registers
>>    (v0-v31, vl, vtype) and vstart to become unspecified.
>
> So the only use case of saving/restoring V regs in __switch_to is an 
> interrupt induced task switch ?

Yes!