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Date:   Mon, 03 Oct 2022 19:54:38 -0700 (PDT)
Subject:     Re: [PATCH v2] RISC-V: Add mvendorid, marchid, and mimpid to /proc/cpuinfo output
In-Reply-To: <20220727043829.151794-1-apatel@ventanamicro.com>
CC:     Paul Walmsley <paul.walmsley@sifive.com>,
        Arnd Bergmann <arnd@arndb.de>, atishp@atishpatra.org,
        nikita.shubin@maquefel.me, heinrich.schuchardt@canonical.com,
        anup@brainfault.org, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, apatel@ventanamicro.com,
        n.shubin@yadro.com
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     apatel@ventanamicro.com
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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.

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 ]---

>
> 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);