linux-kernel - Re: [PATCH 14/19] riscv: hwprobe: Disambiguate vector and xtheadvector in hwprobe

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Message-ID: <20240412-moonshine-acting-0df1a90b86d2@wendy>
Date: Fri, 12 Apr 2024 12:34:01 +0100
From: Conor Dooley <conor.dooley@...rochip.com>
To: Charlie Jenkins <charlie@...osinc.com>
CC: Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Paul Walmsley
	<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec
	<jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, Evan Green
	<evan@...osinc.com>, Clément Léger
	<cleger@...osinc.com>, Jonathan Corbet <corbet@....net>, Shuah Khan
	<shuah@...nel.org>, <linux-riscv@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Palmer Dabbelt
	<palmer@...osinc.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-sunxi@...ts.linux.dev>, <linux-doc@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 14/19] riscv: hwprobe: Disambiguate vector and
 xtheadvector in hwprobe

On Thu, Apr 11, 2024 at 09:11:20PM -0700, Charlie Jenkins wrote:
> Ensure that hwprobe does not flag "v" when xtheadvector is present.
> 
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
>  arch/riscv/kernel/sys_hwprobe.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index 8cae41a502dd..e0a42c851511 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -69,7 +69,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
>  	if (riscv_isa_extension_available(NULL, c))
>  		pair->value |= RISCV_HWPROBE_IMA_C;
>  
> -	if (has_vector())
> +	if (has_vector() && !riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR))

Hmm, I think this is "dangerous". has_vector() is used across the kernel
now in several places for the in-kernel vector. I don't think that
has_vector() should return true for the T-Head stuff given that &
has_vector() should represent the ratified spec. I'll have to think
about this one and how nasty this makes any of the save/restore code
etc.

>  		pair->value |= RISCV_HWPROBE_IMA_V;
>  
>  	/*
> @@ -112,7 +112,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
>  		EXT_KEY(ZACAS);
>  		EXT_KEY(ZICOND);
>  
> -		if (has_vector()) {
> +		if (has_vector() && !riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
>  			EXT_KEY(ZVBB);
>  			EXT_KEY(ZVBC);
>  			EXT_KEY(ZVKB);
> 
> -- 
> 2.44.0
> 

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