Re: [PATCH v4 09/16] riscv: Add Zic64b to cpufeature and hwprobe

Conor Dooley <[email protected]> Fri, 12 Jun 2026 09:41:02 +0100

Newsgroups	dev.linux.lists.sophgo,dev.linux.lists.spacemit,org.infradead.lists.kvm-riscv,org.infradead.lists.linux-riscv,org.kernel.vger.kvm,org.kernel.vger.linux-devicetree,org.kernel.vger.linux-doc,org.kernel.vger.linux-kernel,org.kernel.vger.linux-kselftest
Message-ID	<20260612-frays-feast-e631e3aa047d@wendy>

On Thu, Jun 11, 2026 at 04:12:46PM -0400, Guodong Xu wrote:
> From: Qingwei Hu <[email protected]>
> 
> Zic64b mandates 64-byte naturally aligned cache blocks and is a
> mandatory extension of the RVA22 and RVA23 profiles.  Allocate a
> RISCV_ISA_EXT_ZIC64B id, parse "zic64b" from the ISA string with a
> validate callback that requires each cbom/cbop/cboz cache block size to
> be 64 bytes when it is present, and export it through hwprobe.
> 
> Link: https://lists.riscv.org/g/tech-unprivileged/topic/question_about_zic64b_and/119631059
> Signed-off-by: Qingwei Hu <[email protected]>
> Co-developed-by: Guodong Xu <[email protected]>
> Signed-off-by: Guodong Xu <[email protected]>

> +static int riscv_ext_zic64b_validate(const struct riscv_isa_ext_data *data,
> +				     const unsigned long *isa_bitmap)
> +{
> +	/*
> +	 * Zic64b mandates 64-byte naturally aligned cache blocks; cross-check the
> +	 * cbom/cbop/cboz block-size (when declared) device-tree properties to
> +	 * avoid inconsistency.
> +	 */
> +	if ((riscv_cbom_block_size && riscv_cbom_block_size != 64) ||
> +	    (riscv_cbop_block_size && riscv_cbop_block_size != 64) ||
> +	    (riscv_cboz_block_size && riscv_cboz_block_size != 64)) {
> +		pr_err("Zic64b detected in ISA string, disabling as a CBO block size is not 64 bytes\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}

I'm inclined to object to this, but we don't have validation on ACPI
stuff to be able to mandate that people fill in the rhct entries.
Reviewed-by: Conor Dooley <[email protected]>

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