Re: [PATCH 16/19] riscv: hwprobe: Add vendor extension probing

Conor Dooley
2024-04-12T11:40:14Z

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On Thu, Apr 11, 2024 at 09:11:22PM -0700, Charlie Jenkins wrote:

> +static void hwprobe_isa_vendor_ext0(struct riscv_hwprobe *pair,
> + const struct cpumask *cpus)
> +{
> + int cpu;
> + u64 missing = 0;
> +
> + pair->value = 0;
> +
> + struct riscv_hwprobe mvendorid = {
> + .key = RISCV_HWPROBE_KEY_MVENDORID,
> + .value = 0
> + };
> +
> + hwprobe_arch_id(&mvendorid, cpus);
> +
> + /* Set value to zero if CPUs in the set do not have the same vendor. */
> + if (mvendorid.value == -1ULL)
> + return;
> +
> + /*
> + * Loop through and record vendor extensions that 1) anyone has, and
> + * 2) anyone doesn't have.
> + */
> + for_each_cpu(cpu, cpus) {
> + struct riscv_isainfo *isavendorinfo = &hart_isa_vendor[cpu];
> +
> +#define VENDOR_EXT_KEY(ext) \
> + do { \
> + if (__riscv_isa_vendor_extension_available(isavendorinfo->isa, \
> + RISCV_ISA_VENDOR_EXT_##ext)) \
> + pair->value |= RISCV_HWPROBE_VENDOR_EXT_##ext; \
> + else \
> + missing |= RISCV_HWPROBE_VENDOR_EXT_##ext; \
> + } while (false)
> +
> + /*
> + * Only use VENDOR_EXT_KEY() for extensions which can be exposed to userspace,
> + * regardless of the kernel's configuration, as no other checks, besides
> + * presence in the hart_vendor_isa bitmap, are made.
> + */
> + VENDOR_EXT_KEY(XTHEADVECTOR);

Reading the comment here, I don't think you can do this. All vector
support in userspace is continent on kernel configuration options.

> +
> +#undef VENDOR_EXT_KEY
> + }
> +
> + /* Now turn off reporting features if any CPU is missing it. */
> + pair->value &= ~missing;
> +}

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