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

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;

+}