Re: [PATCH] LoongArch: Refactor the Features output in show_cpuinfo()

[Huacai Chen]

On Tue, Apr 28, 2026 at 6:08 PM Qiang Ma <maqianga@xxxxxxxxxxxxx> wrote:
>
>
> 在 2026/4/28 17:37, Huacai Chen 写道:
> > https://lore.kernel.org/loongarch/20260228102946.4045-1-dongtai.guo@xxxxxxxxx/
> > https://lore.kernel.org/loongarch/20260428075231.2283151-1-maqianga@xxxxxxxxxxxxx/T/#u
> >
> > What make you modify here again and again?
> Sorry, I didn't notice that the relevant patch had already been submitted.
> > Is this function ugly?
> > Is this function has bugs?
> No
> > Or for some other reasons?
>
> I noticed that with the addition of new features to the LoongArch
> architecture,
>
> new features can be conveniently added without constantly needing to add
> if statements, keeping the code concise.
cpuinfo are not always the same as hwcaps, stop please.

Huacai

>
> >
> >
> > Huacai
> >
> > On Tue, Apr 28, 2026 at 3:53 PM Qiang Ma <maqianga@xxxxxxxxxxxxx> wrote:
> >> 1. Adds an hwcap_str[] mapping table, using KERNEL_HWCAP(x)
> >> (i.e., const_ilog2(HWCAP_LOONGARCH_x)) to map HWCAP bits
> >> to corresponding strings;
> >> 2. In show_cpuinfo(), iterates through hwcap_str in a loop,
> >> checks the bitmap of elf_hwcap, and prints the corresponding
> >> feature names;
> >> 3. Maintains the original output semantics (still printing
> >> the same feature names) to facilitate adding new CPU features
> >> in the future.
> >>
> >> Signed-off-by: Qiang Ma <maqianga@xxxxxxxxxxxxx>
> >> ---
> >>   arch/loongarch/kernel/proc.c | 60 ++++++++++++++++--------------------
> >>   1 file changed, 26 insertions(+), 34 deletions(-)
> >>
> >> diff --git a/arch/loongarch/kernel/proc.c b/arch/loongarch/kernel/proc.c
> >> index d4ce5b585453..1188bffd66b6 100644
> >> --- a/arch/loongarch/kernel/proc.c
> >> +++ b/arch/loongarch/kernel/proc.c
> >> @@ -12,9 +12,32 @@
> >>   #include <asm/idle.h>
> >>   #include <asm/processor.h>
> >>   #include <asm/time.h>
> >> +#include <asm/cpufeature.h>
> >> +
> >> +#define KERNEL_HWCAP(x)  const_ilog2(HWCAP_LOONGARCH_ ## x)
> >> +static const char *const hwcap_str[] = {
> >> +       [KERNEL_HWCAP(CPUCFG)]          = "cpucfg",
> >> +       [KERNEL_HWCAP(LAM)]             = "lam",
> >> +       [KERNEL_HWCAP(LAM_BH)]          = "lam_bh",
> >> +       [KERNEL_HWCAP(UAL)]             = "ual",
> >> +       [KERNEL_HWCAP(FPU)]             = "fpu",
> >> +       [KERNEL_HWCAP(LSX)]             = "lsx",
> >> +       [KERNEL_HWCAP(LASX)]            = "lasx",
> >> +       [KERNEL_HWCAP(CRC32)]           = "crc32",
> >> +       [KERNEL_HWCAP(COMPLEX)]         = "complex",
> >> +       [KERNEL_HWCAP(CRYPTO)]          = "crypto",
> >> +       [KERNEL_HWCAP(LVZ)]             = "lvz",
> >> +       [KERNEL_HWCAP(LBT_X86)]         = "lbt_x86",
> >> +       [KERNEL_HWCAP(LBT_ARM)]         = "lbt_arm",
> >> +       [KERNEL_HWCAP(LBT_MIPS)]        = "lbt_mips",
> >> +       [KERNEL_HWCAP(PTW)]             = "ptw",
> >> +       [KERNEL_HWCAP(LSPW)]            = "lspw",
> >> +       [KERNEL_HWCAP(SCQ)]             = "scq",
> >> +};
> >>
> >>   static int show_cpuinfo(struct seq_file *m, void *v)
> >>   {
> >> +       unsigned int i;
> >>          unsigned long n = (unsigned long) v - 1;
> >>          unsigned int isa = cpu_data[n].isa_level;
> >>          unsigned int prid = cpu_data[n].processor_id;
> >> @@ -60,40 +83,9 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> >>          seq_puts(m, "\n");
> >>
> >>          seq_puts(m, "Features\t\t:");
> >> -       if (cpu_has_cpucfg)
> >> -               seq_puts(m, " cpucfg");
> >> -       if (cpu_has_lam)
> >> -               seq_puts(m, " lam");
> >> -       if (cpu_has_lam_bh)
> >> -               seq_puts(m, " lam_bh");
> >> -       if (cpu_has_scq)
> >> -               seq_puts(m, " scq");
> >> -       if (cpu_has_ual)
> >> -               seq_puts(m, " ual");
> >> -       if (cpu_has_fpu)
> >> -               seq_puts(m, " fpu");
> >> -       if (cpu_has_lsx)
> >> -               seq_puts(m, " lsx");
> >> -       if (cpu_has_lasx)
> >> -               seq_puts(m, " lasx");
> >> -       if (cpu_has_crc32)
> >> -               seq_puts(m, " crc32");
> >> -       if (cpu_has_complex)
> >> -               seq_puts(m, " complex");
> >> -       if (cpu_has_crypto)
> >> -               seq_puts(m, " crypto");
> >> -       if (cpu_has_ptw)
> >> -               seq_puts(m, " ptw");
> >> -       if (cpu_has_lspw)
> >> -               seq_puts(m, " lspw");
> >> -       if (cpu_has_lvz)
> >> -               seq_puts(m, " lvz");
> >> -       if (cpu_has_lbt_x86)
> >> -               seq_puts(m, " lbt_x86");
> >> -       if (cpu_has_lbt_arm)
> >> -               seq_puts(m, " lbt_arm");
> >> -       if (cpu_has_lbt_mips)
> >> -               seq_puts(m, " lbt_mips");
> >> +       for (i = 0; i < ARRAY_SIZE(hwcap_str); i++)
> >> +               if (elf_hwcap & (1 << i))
> >> +                       seq_printf(m, " %s", hwcap_str[i]);
> >>          seq_puts(m, "\n");
> >>
> >>          seq_printf(m, "Hardware Watchpoint\t: %s", str_yes_no(cpu_has_watch));
> >> --
> >> 2.20.1
> >>