Re: [PATCH] RISC-V: Add mvendorid, marchid, and mimpid to /proc/cpuinfo output

From: Nikita Shubin
Date: Tue Jun 21 2022 - 03:41:24 EST


Hello Anup!

On Mon, 20 Jun 2022 17:25:49 +0530
Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:

> Identifying the underlying RISC-V implementation can be important
> for some of the user space applications. For example, the perf tool
> uses arch specific CPU implementation id (i.e. CPUID) to select a
> JSON file describing custom perf events on a CPU.
>
> Currently, there is no way to identify RISC-V implementation so we
> add mvendorid, marchid, and mimpid to /proc/cpuinfo output.

Tested on Sifive Unmatched:

localhost / # cat /proc/cpuinfo
processor : 0
hart : 4
isa : rv64imafdc
mmu : sv39
uarch : sifive,bullet0
mvendorid : 0x489
marchid : 0x8000000000000007
mimpid : 0x20181004

processor : 1
hart : 1
isa : rv64imafdc
mmu : sv39
uarch : sifive,bullet0
mvendorid : 0x489
marchid : 0x8000000000000007
mimpid : 0x20181004

processor : 2
hart : 2
isa : rv64imafdc
mmu : sv39
uarch : sifive,bullet0
mvendorid : 0x489
marchid : 0x8000000000000007
mimpid : 0x20181004

processor : 3
hart : 3
isa : rv64imafdc
mmu : sv39
uarch : sifive,bullet0
mvendorid : 0x489
marchid : 0x8000000000000007
mimpid : 0x20181004

mvendorid, marchid values match the register description in u74 manual.

mimpid seems to be ok, through i can't find exact in U74/Unmatched docs.

Tested-by: Nikita Shubin <n.shubin@xxxxxxxxx>

>
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> ---
> arch/riscv/kernel/cpu.c | 51
> +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51
> insertions(+)
>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index fba9e9f46a8c..c037b8691bbb 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -3,10 +3,13 @@
> * Copyright (C) 2012 Regents of the University of California
> */
>
> +#include <linux/cpu.h>
> #include <linux/init.h>
> #include <linux/seq_file.h>
> #include <linux/of.h>
> +#include <asm/csr.h>
> #include <asm/hwcap.h>
> +#include <asm/sbi.h>
> #include <asm/smp.h>
> #include <asm/pgtable.h>
>
> @@ -64,6 +67,50 @@ int riscv_of_parent_hartid(struct device_node
> *node) }
>
> #ifdef CONFIG_PROC_FS
> +
> +struct riscv_cpuinfo {
> + unsigned long mvendorid;
> + unsigned long marchid;
> + unsigned long mimpid;
> +};
> +static DEFINE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
> +
> +static int riscv_cpuinfo_starting(unsigned int cpu)
> +{
> + struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
> +
> +#if defined(CONFIG_RISCV_SBI)
> + ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> + ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
> + ci->mimpid = sbi_spec_is_0_1() ? 0 : sbi_get_mimpid();
> +#elif defined(CONFIG_RISCV_M_MODE)
> + ci->mvendorid = csr_read(CSR_MVENDORID);
> + ci->marchid = csr_read(CSR_MARCHID);
> + ci->mimpid = csr_read(CSR_MIMPID);
> +#else
> + ci->mvendorid = 0;
> + ci->marchid = 0;
> + ci->mimpid = 0;
> +#endif
> +
> + return 0;
> +}
> +
> +static int __init riscv_cpuinfo_init(void)
> +{
> + int ret;
> +
> + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
> "riscv/cpuinfo:starting",
> + riscv_cpuinfo_starting, NULL);
> + if (ret < 0) {
> + pr_err("cpuinfo: failed to register hotplug
> callbacks.\n");
> + return ret;
> + }
> +
> + return 0;
> +}
> +device_initcall(riscv_cpuinfo_init);
> +
> #define __RISCV_ISA_EXT_DATA(UPROP, EXTID) \
> { \
> .uprop = #UPROP, \
> @@ -178,6 +225,7 @@ static int c_show(struct seq_file *m, void *v)
> {
> unsigned long cpu_id = (unsigned long)v - 1;
> struct device_node *node = of_get_cpu_node(cpu_id, NULL);
> + struct riscv_cpuinfo *ci = per_cpu_ptr(&riscv_cpuinfo,
> cpu_id); const char *compat, *isa;
>
> seq_printf(m, "processor\t: %lu\n", cpu_id);
> @@ -188,6 +236,9 @@ static int c_show(struct seq_file *m, void *v)
> if (!of_property_read_string(node, "compatible", &compat)
> && strcmp(compat, "riscv"))
> seq_printf(m, "uarch\t\t: %s\n", compat);
> + seq_printf(m, "mvendorid\t: 0x%lx\n", ci->mvendorid);
> + seq_printf(m, "marchid\t\t: 0x%lx\n", ci->marchid);
> + seq_printf(m, "mimpid\t\t: 0x%lx\n", ci->mimpid);
> seq_puts(m, "\n");
> of_node_put(node);
>