Messages in this thread Patch in this message | | | From | Anup Patel <> | Date | Wed, 27 Jul 2022 15:36:33 +0530 | Subject | Re: [PATCH v2] RISC-V: Add mvendorid, marchid, and mimpid to /proc/cpuinfo output |
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On Wed, Jul 27, 2022 at 2:25 PM Ben Dooks <ben.dooks@codethink.co.uk> wrote: > > On 27/07/2022 05:38, Anup Patel 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(+) > > > > 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(); > > how about: > > if (IS_ENABLED(CONFIG_RISCV_SBI)) { > ... > } ... { > > or maybe even: > > > if (IS_ENABLED(CONFIG_RISCV_SBI)) { > if (sbi_spec_is_0_1()) { > ... > } > } ... { > > would mean better compile coverage (at the slight exepnese of > having "false" sbi_spec_is_0_1() implemenation
Most of the sbi_xyz() functions are not available for NoMMU kernel so using "if (IS_ENABLED())" results in compile error.
> > > +#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 > > Would it be easier to zero out all the fields first and then fill them > in if supported?
Clearing out fields before "#if" ladder results in dead assignments.
Regards, Anup
> > > + > > + 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); > > > > > -- > Ben Dooks http://www.codethink.co.uk/ > Senior Engineer Codethink - Providing Genius > > https://www.codethink.co.uk/privacy.html
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