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

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Message-ID: <CAEyhmHTV_AkZ=hFN4aCisBbecTtOahPaMGmC8BtfD7p_9OAEJw@mail.gmail.com>
Date: Wed, 26 Nov 2025 13:27:17 +0800
From: Hengqi Chen <hengqi.chen@...il.com>
To: Qiang Ma <maqianga@...ontech.com>
Cc: chenhuacai@...nel.org, kernel@...0n.name, loongarch@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Correct the calculation logic of thread_count

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.
>
> 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);

You have `dm->length >= 0x30` below but the memory load already done here.

> +       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
>
>