Re: [PATCH v2 RESEND] loongarch: retrieve CPU package ID from PPTT when available

Hi Rong,

在 2026/7/5 17:36, Rong Bao 写道:
> Currently, the LoongArch CPU topology initialization code calculates
> each core's package ID by dividing its physical ID by
> loongson_sysconf.cores_per_package. This relies on the assumption that
> cores_per_package counts in the same domain as physical IDs.
> 
> On Loongson 3B6000 (XB612B0V_1.2), cores_per_package matches the visible
> core count -- 24 in this case. However, the physical IDs range from 0 to
> 31 in a noncontinuous fashion:
> 
>          $ cat /proc/cpuinfo | grep -i -F 'global_id'
>          global_id               : 0
>          global_id               : 1
>          global_id               : 4
>          global_id               : 5
>          global_id               : 6
>          global_id               : 7
>          global_id               : 8
>          global_id               : 9
>          global_id               : 10
>          global_id               : 11
>          global_id               : 14
>          global_id               : 15
>          global_id               : 16
>          global_id               : 17
>          global_id               : 20
>          global_id               : 21
>          global_id               : 22
>          global_id               : 23
>          global_id               : 26
>          global_id               : 27
>          global_id               : 28
>          global_id               : 29
>          global_id               : 30
>          global_id               : 31
> 
> Retrieve the exact package ID from ACPI PPTT when available, in the same
> style as retrieving the core ID and thread ID in parse_acpi_topology().
> Use this information in loongson_init_secondary() when PPTT readout is
> successful. The original division logic is kept as a fallback.
> 
> Meanwhile, since some code paths like loongson3_cpufreq expect a
> continuous integer sequence of package IDs in [0, MAX_PACKAGES) when
> retrieving from cpu_data[], we also canonicalize the package ID to be
> filled in parse_acpi_topology() to meet such an expectation.
> 
> Cc: [email protected]
> Co-developed-by: Xi Ruoyao <[email protected]>
> Signed-off-by: Xi Ruoyao <[email protected]>
> Signed-off-by: Rong Bao <[email protected]>
Tested good on my Loongson XB612B0_V1.0 with an 8-core 3B6000:

Architecture:                loongarch64
   CPU op-mode(s):            32-bit, 64-bit
   Address sizes:             48 bits physical, 48 bits virtual
   Byte Order:                Little Endian
CPU(s):                      16
   On-line CPU(s) list:       0-15
Model name:                  Loongson-3B6000
   CPU family:                Loongson-64bit
   Model:                     0x10
   Thread(s) per core:        2
   Core(s) per socket:        8
   Socket(s):                 1
   BogoMIPS:                  4600.00
   Flags:                     cpucfg lam lam_bh scq ual fpu lsx lasx 
crc32 complex crypto lspw lvz lbt_x86 lbt_arm lbt_mips
Caches (sum of all):
   L1d:                       512 KiB (8 instances)
   L1i:                       512 KiB (8 instances)
   L2:                        2 MiB (8 instances)
   L3:                        32 MiB (1 instance)
NUMA:
   NUMA node(s):              1
   NUMA node0 CPU(s):         0-15
Vulnerabilities:
   Gather data sampling:      Not affected
   Ghostwrite:                Not affected
   Indirect target selection: Not affected
   Itlb multihit:             Not affected
   L1tf:                      Not affected
   Mds:                       Not affected
   Meltdown:                  Not affected
   Mmio stale data:           Not affected
   Old microcode:             Not affected
   Reg file data sampling:    Not affected
   Retbleed:                  Not affected
   Spec rstack overflow:      Not affected
   Spec store bypass:         Not affected
   Spectre v1:                Mitigation; __user pointer sanitization
   Spectre v2:                Not affected
   Srbds:                     Not affected
   Tsa:                       Not affected
   Tsx async abort:           Not affected
   Vmscape:                   Not affected

With that:

Tested-by: Mingcong Bai <[email protected]>

Best Regards,
Mingcong Bai