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Date:   Mon, 03 Oct 2022 21:35:25 -0700 (PDT)
Subject:     Re: [PATCH v2] RISC-V: Add mvendorid, marchid, and mimpid to /proc/cpuinfo output
In-Reply-To: <CAAhSdy0mhfva7gGvH9_w2MpTO3zN7Mutf8MGxCniwwdAmFpekg@mail.gmail.com>
CC:     apatel@ventanamicro.com, Paul Walmsley <paul.walmsley@sifive.com>,
        Arnd Bergmann <arnd@arndb.de>, atishp@atishpatra.org,
        nikita.shubin@maquefel.me, heinrich.schuchardt@canonical.com,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        n.shubin@yadro.com
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     anup@brainfault.org
Message-ID: <mhng-29532f94-476b-450e-b758-209e8b7c9fc7@palmer-ri-x1c9>
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On Mon, 03 Oct 2022 20:44:54 PDT (-0700), anup@brainfault.org wrote:
> On Tue, Oct 4, 2022 at 8:24 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>>
>> On Tue, 26 Jul 2022 21:38:29 PDT (-0700), apatel@ventanamicro.com 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@ventanamicro.com>
>> > Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
>> > Tested-by: Nikita Shubin <n.shubin@yadro.com>
>> > ---
>> > 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);