Re: [PATCH v5 0/4] Building PPTT with root node and identical implementation flag

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, May 23, 2025 at 11:26:50AM +0100, Alireza Sanaee wrote:
> OS like Linux is using PPTT processor node's identical implementation
> flag [1] to infer whether the whole system or a certain CPU cluster is
> homogeneous or not [2]. QEMU currently only support building homogeneous
> system, set the flag to indicate the fact. Build a root node in PPTT for
> indicates the identical implementation which is needed for a
> multi-socket system. Update the related PPTT tables as well.
> 
> [1] ACPI 6.5 Table 5.158: Processor Structure Flags
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/acpi/pptt.c?h=v6.11-rc1#n810
> 
> History:
>     * v4->v5: fixed a typo
> 
>     * v3->v4: PPTT rev to 2
> 
>     * v2->v3: rebase to 10
> 
> Alireza Sanaee (2):
>   hw/acpi/aml-build: Build a root node in the PPTT table
>   tests: virt: Update expected ACPI tables for virt test
> 
> Yicong Yang (2):
>   tests: virt: Allow changes to PPTT test table
>   hw/acpi/aml-build: Set identical implementation flag for PPTT
>     processor nodes
> 
>  hw/acpi/aml-build.c                           |  24 +++++++++++++++---
>  tests/data/acpi/aarch64/virt/PPTT             | Bin 76 -> 96 bytes
>  .../data/acpi/aarch64/virt/PPTT.acpihmatvirt  | Bin 156 -> 176 bytes
>  tests/data/acpi/aarch64/virt/PPTT.topology    | Bin 336 -> 356 bytes
>  4 files changed, 20 insertions(+), 4 deletions(-)


This interacts weirdly with loongarch. I tried applying patches
on top of that, and on loongarch, I see:

-[0F0h 0240 004h]       Flags (decoded below) : 00000000
+[0F0h 0240 004h]       Flags (decoded below) : 0000000E
                             Physical package : 0
-                     ACPI Processor ID valid : 0
-                       Processor is a thread : 0
-                              Node is a leaf : 0
+                     ACPI Processor ID valid : 1
+                       Processor is a thread : 1
+                              Node is a leaf : 1
                     Identical Implementation : 0


I'm sending a pull request later today. Once merged, pls
rebase on top of that, updating loongarch as appropriate
and repost copying relevant people.

Cc Bibo Mao for more insight.


> -- 
> 2.34.1