linux-kernel - Re: [PATCH] LoongArch: Correct the calculation logic of thread

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Message-ID: <CAAhV-H4EOTwn3fSJHWOkahgO3VHPGN9k9mbY7akpHDny_sBOsQ@mail.gmail.com>
Date: Wed, 26 Nov 2025 12:49:00 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Qiang Ma <maqianga@...ontech.com>
Cc: kernel@...0n.name, loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Correct the calculation logic of thread_count

Hi, Qiang,

On Wed, Nov 26, 2025 at 10:37 AM Qiang Ma <maqianga@...ontech.com> wrote:
>
> For thread_count, the current calculation method has a maximum of 255,
> which may not be sufficient in the future. Therefore, we are correcting
> it now.
I think you should contact the Loongson BIOS team to confirm they will do so.

And we can hardly meet the case that one socket contains more than 256
cores (this is different from the case MAX_CPUS > 256)

Huacai

>
> Reference: SMBIOS Specification, 7.5 Processor Information (Type 4)[1]
>
> [1]: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.9.0.pdf
>
> Signed-off-by: Qiang Ma <maqianga@...ontech.com>
> ---
>  arch/loongarch/kernel/setup.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
> index 25a87378e48e..760f5ce44384 100644
> --- a/arch/loongarch/kernel/setup.c
> +++ b/arch/loongarch/kernel/setup.c
> @@ -56,6 +56,7 @@
>  #define SMBIOS_FREQLOW_MASK            0xFF
>  #define SMBIOS_CORE_PACKAGE_OFFSET     0x23
>  #define SMBIOS_THREAD_PACKAGE_OFFSET   0x25
> +#define SMBIOS_THREAD_PACKAGE_2_OFFSET 0x2E
>  #define LOONGSON_EFI_ENABLE            (1 << 3)
>
>  unsigned long fw_arg0, fw_arg1, fw_arg2;
> @@ -120,13 +121,19 @@ static void __init parse_cpu_table(const struct dmi_header *dm)
>  {
>         long freq_temp = 0;
>         char *dmi_data = (char *)dm;
> +       u8 thread_count;
> +       u16 thread_count2;
>
>         freq_temp = ((*(dmi_data + SMBIOS_FREQHIGH_OFFSET) << 8) +
>                         ((*(dmi_data + SMBIOS_FREQLOW_OFFSET)) & SMBIOS_FREQLOW_MASK));
>         cpu_clock_freq = freq_temp * 1000000;
>
>         loongson_sysconf.cpuname = (void *)dmi_string_parse(dm, dmi_data[16]);
> -       loongson_sysconf.cores_per_package = *(dmi_data + SMBIOS_THREAD_PACKAGE_OFFSET);
> +       thread_count = *(dmi_data + SMBIOS_THREAD_PACKAGE_OFFSET);
> +       thread_count2 = *(u16 *)(dmi_data + SMBIOS_THREAD_PACKAGE_2_OFFSET);
> +       if (thread_count != 0)
> +               loongson_sysconf.cores_per_package = dm->length >= 0x30 && thread_count == 0xFF ?
> +                                                    thread_count2 : thread_count;
>
>         pr_info("CpuClock = %llu\n", cpu_clock_freq);
>  }
> --
> 2.20.1
>