Re: [PATCH v2] RISC-V: Add mvendorid, marchid, and mimpid to /proc/cpuinfo output

From: Palmer Dabbelt
Date: Tue Oct 04 2022 - 00:35:33 EST

On Mon, 03 Oct 2022 20:44:54 PDT (-0700), anup@xxxxxxxxxxxxxx wrote:
On Tue, Oct 4, 2022 at 8:24 AM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:

On Tue, 26 Jul 2022 21:38:29 PDT (-0700), 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.
>
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@xxxxxxxxxxxxx>
> Tested-by: Nikita Shubin <n.shubin@xxxxxxxxx>
> ---
> Changes since v1:
> - Use IS_ENABLED() to check CONFIG defines
> - Added RB and TB tags in commit description
> ---
> arch/riscv/kernel/cpu.c | 51 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 51 insertions(+)

Sorry for being slow on this one. I'd been worried about sticking more
stuff into /proc/cpuinfo, as having the only user interface for these
involve parsing /proc/cpuinfo is really just a recipe for disaster. I
didn't get around do doing something better, though, and waiting for
another release seems kind of silly.

In addition to being useful for perf tool, printing vendor and
implementation details in /proc/cpuinfo is a very useful info.

Users can easily know the underlying CPU implementer using
"cat /proc/cpuinfo".


I was going to go put this on for-next, but it looks like it's causing
kasan boot failures. I'm not actually quite sure how this is triggering
these, at least based on the backtrace, but there's a bunch of them and
boot hangs.

Here's the first of them:

[ 3.830416] Hardware name: riscv-virtio,qemu (DT)
[ 3.830828] epc : kasan_check_range+0x116/0x14c
[ 3.832377] ra : memset+0x1e/0x4c
[ 3.832699] epc : ffffffff8026468e ra : ffffffff80264d6e sp : ff600000832afa60
[ 3.833051] gp : ffffffff81d800a0 tp : ff600000831d2400 t0 : ff60000083224360
[ 3.833397] t1 : ffebfffefffef000 t2 : 0000000000000000 s0 : ff600000832afa90
[ 3.833811] s1 : 0000000000000004 a0 : 0000000000000010 a1 : 0000000000000004
[ 3.834210] a2 : 0000000000000001 a3 : ffffffff801fa22c a4 : ff5ffffffff78000
[ 3.834558] a5 : ffebfffefffef000 a6 : ffebfffefffef001 a7 : ff5ffffffff78003
[ 3.834931] s2 : ff5ffffffff78000 s3 : 0000000000000000 s4 : ffffffff815b59b0
[ 3.835292] s5 : ffffffff81d815e0 s6 : 0000000000000000 s7 : 0000000000000008
[ 3.836400] s8 : ffffffff81d8b0e0 s9 : 0000000000000000 s10: 0000000000000008
[ 3.836817] s11: ff5ffffffff78000 t3 : 0000000000000000 t4 : ffebfffefffef000
[ 3.837154] t5 : ffebfffefffef001 t6 : 0000000000000002
[ 3.837471] status: 0000000000000120 badaddr: ffebfffefffef000 cause: 000000000000000d
[ 3.837933] [<ffffffff801fa22c>] pcpu_alloc+0x494/0x838
[ 3.838324] [<ffffffff801fa5fc>] __alloc_percpu+0x14/0x1c
[ 3.838623] [<ffffffff800930fa>] __percpu_init_rwsem+0x1a/0x98
[ 3.838995] [<ffffffff80286c5a>] alloc_super+0x148/0x3da
[ 3.839631] [<ffffffff80287af2>] sget_fc+0x90/0x2c4
[ 3.840240] [<ffffffff80288498>] get_tree_nodev+0x24/0xa4
[ 3.840598] [<ffffffff801e919a>] shmem_get_tree+0x14/0x1c
[ 3.840891] [<ffffffff80286436>] vfs_get_tree+0x3a/0x11a
[ 3.841172] [<ffffffff802ba746>] path_mount+0x2ea/0xb44
[ 3.841468] [<ffffffff802bb69a>] sys_mount+0x1b2/0x270
[ 3.841790] [<ffffffff80003d1c>] ret_from_syscall+0x0/0x2
[ 3.842480] ---[ end trace 0000000000000000 ]---

Sure, I will try to fix this ASAP.

Are you willing to take this if the above issue is fixed ?

I still think the other interface is better, but it's taking too long and some stuff is blocked on getting these to userspace so I'm fine with it.


Regards,
Anup


>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index fba9e9f46a8c..04bcc91c91ea 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 IS_ENABLED(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 IS_ENABLED(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);