linux-kernel - Re: [PATCH v2 05/13] riscv: cpufeature: extend riscv_cpufeature_patch

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Date:   Mon, 5 Dec 2022 19:37:53 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Jisheng Zhang <jszhang@...nel.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Andrew Jones <ajones@...tanamicro.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 05/13] riscv: cpufeature: extend
 riscv_cpufeature_patch_func to all ISA extensions

On Mon, Dec 05, 2022 at 01:46:24AM +0800, Jisheng Zhang wrote:
> make the riscv_cpufeature_patch_func() scan all ISA extensions rather
> than limited feature macros.

Certainly looks like a nice cleanup. Perhaps for the changelog,
something along the lines of:

"riscv_cpufeature_patch_func() currently only scans a limited set of
cpufeatures, explicitly defined with macros. Extend it to probe for all
ISA extensions"

> 
> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
> Reviewed-by: Heiko Stuebner <heiko@...ech.de>
> ---
>  arch/riscv/include/asm/errata_list.h |  9 ++--
>  arch/riscv/kernel/cpufeature.c       | 73 +++++-----------------------
>  2 files changed, 15 insertions(+), 67 deletions(-)

> @@ -311,25 +264,23 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
>  	for (alt = begin; alt < end; alt++) {
>  		if (alt->vendor_id != 0)
>  			continue;
> -		if (alt->errata_id >= CPUFEATURE_NUMBER) {
> -			WARN(1, "This feature id:%d is not in kernel cpufeature list",
> +		if (alt->errata_id >= RISCV_ISA_EXT_MAX) {
> +			WARN(1, "This extension id:%d is not in ISA extension list",
>  				alt->errata_id);
>  			continue;
>  		}
>  
> -		tmp = (1U << alt->errata_id);
> -		if (cpu_req_feature & tmp) {
> -			/* do the basic patching */
> -			patch_text_nosync(alt->old_ptr, alt->alt_ptr,
> -					  alt->alt_len);
> +		if (!__riscv_isa_extension_available(NULL, alt->errata_id))
> +			continue;
>  
> -			riscv_alternative_fix_auipc_jalr(alt->old_ptr,
> -							 alt->alt_len,
> -							 alt->old_ptr - alt->alt_ptr);
> -			riscv_alternative_fix_jal(alt->old_ptr,
> -						  alt->alt_len,
> -						  alt->old_ptr - alt->alt_ptr);
> -		}
> +		/* do the basic patching */
> +		patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
> +		riscv_alternative_fix_auipc_jalr(alt->old_ptr,
> +						 alt->alt_len,
> +						 alt->old_ptr - alt->alt_ptr);
> +		riscv_alternative_fix_jal(alt->old_ptr,
> +					  alt->alt_len,
> +					  alt->old_ptr - alt->alt_ptr);

nit:
Now that you've dropped a level of indent, can alt->alt_len move up a
line?

Thanks,
Conor.


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