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

[Anup Patel]

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 ?

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);