Messages in this thread | | | Date | Wed, 27 Jul 2022 11:12:14 +0100 | Subject | Re: [PATCH v2] RISC-V: Add mvendorid, marchid, and mimpid to /proc/cpuinfo output | From | Ben Dooks <> |
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On 27/07/2022 11:06, Anup Patel wrote: > 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.
How about defining "false" versions for no-mmu case and try and avoid these #if mountains?
>> >>> +#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.
Not sure which is worse here, the #if ladder or some possibly dead assignments.
-- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius
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