Re: [PATCH v3 13/15] riscv: cpufeature: Introduce ISA bases bitmap and rva23u64 detection

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Detection of the RVA23U64 profile fails on compliant platforms because it strictly requires the unratified `RISCV_ISA_EXT_B` bundle instead of the formally ratified bitmanip extensions (`Zba`, `Zbb`, `Zbs`).
--

commit 6676802d36b9823a1e8e9c6f39247c2722210748
Author: Guodong Xu <docular.xu@gmail.com>
riscv: cpufeature: Introduce ISA bases bitmap and rva23u64 detection

This commit introduces a per-hart and host-wide bitmap of conformant ISA
profile bases, computed at init time. It also registers the initialization
as a subsys_initcall to ensure prerequisite user pmlen checks are complete
before evaluating RVA23U64 conformity.

> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 79ff431768139..15b708da98a1c 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c

[ ... ]

> @@ -1321,3 +1324,90 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
> +static void riscv_set_isa_bases(unsigned long *bases, const unsigned long *isa_bitmap)
> +{

[ ... ]

> +	/* RVA23U64 */
> +
> +	/* Supm with PMLEN=7 */
> +	if (!riscv_have_user_pmlen(7))
> +		return;
> +
> +	__set_bit(RISCV_ISA_EXT_F, ext_mask);
> +	__set_bit(RISCV_ISA_EXT_D, ext_mask);
> +	__set_bit(RISCV_ISA_EXT_C, ext_mask);
> +	__set_bit(RISCV_ISA_EXT_B, ext_mask);

[Severity: Medium]
Will this cause RVA23U64 detection to fail on compliant hardware?

The RVA23U64 profile mandates the Zba, Zbb, and Zbs extensions.
However, the single-letter B extension was never formally ratified, so
compliant device trees typically advertise the individual bitmanip
extensions (zba, zbb, zbs) instead of the umbrella b bundle.

Since riscv_resolve_isa() does not perform reverse mapping to synthesize
the RISCV_ISA_EXT_B bit when its subsets are present, the subsequent
bitmap_subset() check in riscv_set_isa_bases() will fail. This would
prevent the kernel from detecting and exposing the RVA23U64 base profile.

Should this require the individual Zba, Zbb, and Zbs extensions instead
of RISCV_ISA_EXT_B?

> +	__set_bit(RISCV_ISA_EXT_ZICSR, ext_mask);
> +	__set_bit(RISCV_ISA_EXT_ZICNTR, ext_mask);

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260603-rva23u64-hwprobe-v2-v3-0-5529a7b28384@gmail.com?part=13