linux-kernel - Re: [PATCH v12 06/17] riscv: Reset vector register

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Message-ID: <2331455.NG923GbCHz@diego>
Date:   Fri, 20 Jan 2023 13:20:09 +0100
From:   Heiko Stübner <heiko@...ech.de>
To:     linux-riscv@...ts.infradead.org
Cc:     Guo Ren <guoren@...ux.alibaba.com>,
        Vincent Chen <vincent.chen@...ive.com>,
        Han-Kuan Chen <hankuan.chen@...ive.com>,
        Greentime Hu <greentime.hu@...ive.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        Guo Ren <guoren@...nel.org>,
        Chris Stillson <stillson@...osinc.com>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
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        Barret Rhoden <brho@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
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        Chris Stillson <stillson@...osinc.com>
Subject: Re: [PATCH v12 06/17] riscv: Reset vector register

Am Mittwoch, 21. September 2022, 23:43:48 CET schrieb Chris Stillson:
> @@ -431,6 +431,29 @@ ENTRY(reset_regs)
>  	csrw	fcsr, 0
>  	/* note that the caller must clear SR_FS */
>  #endif /* CONFIG_FPU */
> +
> +#ifdef CONFIG_VECTOR
> +	csrr	t0, CSR_MISA
> +	li	t1, COMPAT_HWCAP_ISA_V
> +	and	t0, t0, t1
> +	beqz	t0, .Lreset_regs_done
> +
> +	/*
> +	 * Clear vector registers and reset vcsr
> +	 * VLMAX has a defined value, VLEN is a constant,
> +	 * and this form of vsetvli is defined to set vl to VLMAX.
> +	 */
> +	li	t1, SR_VS
> +	csrs	CSR_STATUS, t1
> +	csrs	CSR_VCSR, x0
> +	vsetvli t1, x0, e8, m8, ta, ma
> +	vmv.v.i v0, 0
> +	vmv.v.i v8, 0
> +	vmv.v.i v16, 0
> +	vmv.v.i v24, 0
> +	/* note that the caller must clear SR_VS */
> +#endif /* CONFIG_VECTOR */
> +
>  .Lreset_regs_done:

Not sure how much they go together, but the #ifdef CONFIG_FPU block above
your new VECTOR block also jumps to the same .Lreset_regs_done, so with
the patch as is the vector-reset block is never reached in the !FPU case.

So maybe making them independent of each other might prevent issues
down the roead.