linux-kernel - Re: [PATCH v3 00/16] arch_topology: Updates to add socket support and fix cluster ids

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Date:   Wed, 1 Jun 2022 11:49:07 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v3 00/16] arch_topology: Updates to add socket support and
 fix cluster ids

Hi Sudeep,

On 5/25/22 4:14 PM, Sudeep Holla wrote:
> This version updates cacheinfo to populate and use the information from
> there for all the cache topology. Sorry for posting in the middle of
> merge window but better to get this tested earlier so that it is ready
> for next merge window.
> 
> This series intends to fix some discrepancies we have in the CPU topology
> parsing from the device tree /cpu-map node. Also this diverges from the
> behaviour on a ACPI enabled platform. The expectation is that both DT
> and ACPI enabled systems must present consistent view of the CPU topology.
> 
> Currently we assign generated cluster count as the physical package identifier
> for each CPU which is wrong. The device tree bindings for CPU topology supports
> sockets to infer the socket or physical package identifier for a given CPU.
> Also we don't check if all the cores/threads belong to the same cluster before
> updating their sibling masks which is fine as we don't set the cluster id yet.
> 
> These changes also assigns the cluster identifier as parsed from the device tree
> cluster nodes within /cpu-map without support for nesting of the clusters.
> Finally, it also add support for socket nodes in /cpu-map. With this the
> parsing of exact same information from ACPI PPTT and /cpu-map DT node
> aligns well.
> 
> The only exception is that the last level cache id information can be
> inferred from the same ACPI PPTT while we need to parse CPU cache nodes
> in the device tree.
> 
> P.S: I have not cc-ed Greg and Rafael so that all the users of arch_topology
> agree with the changes first before we include them.
> 
> v2[2]->v3:
> 	- Dropped support to get the device node for the CPU's LLC
> 	- Updated cacheinfo to support calling of detect_cache_attributes
> 	  early in smp_prepare_cpus stage
> 	- Added support to check if LLC is valid and shared in the cacheinfo
> 	- Used the same in arch_topology
> 
> v1[1]->v2[2]:
> 	- Updated ID validity check include all non-negative value
> 	- Added support to get the device node for the CPU's last level cache
> 	- Added support to build llc_sibling on DT platforms
> 
> [1] https://lore.kernel.org/lkml/20220513095559.1034633-1-sudeep.holla@arm.com
> [2] https://lore.kernel.org/lkml/20220518093325.2070336-1-sudeep.holla@arm.com
> 
> Sudeep Holla (16):
>    cacheinfo: Use of_cpu_device_node_get instead cpu_dev->of_node
>    cacheinfo: Add helper to access any cache index for a given CPU
>    cacheinfo: Move cache_leaves_are_shared out of CONFIG_OF
>    cacheinfo: Add support to check if last level cache(LLC) is valid or shared
>    cacheinfo: Allow early detection and population of cache attributes
>    arch_topology: Add support to parse and detect cache attributes
>    arch_topology: Use the last level cache information from the cacheinfo
>    arm64: topology: Remove redundant setting of llc_id in CPU topology
>    arch_topology: Drop LLC identifier stash from the CPU topology
>    arch_topology: Set thread sibling cpumask only within the cluster
>    arch_topology: Check for non-negative value rather than -1 for IDs validity
>    arch_topology: Avoid parsing through all the CPUs once a outlier CPU is found
>    arch_topology: Don't set cluster identifier as physical package identifier
>    arch_topology: Drop unnecessary check for uninitialised package_id
>    arch_topology: Set cluster identifier in each core/thread from /cpu-map
>    arch_topology: Add support for parsing sockets in /cpu-map
> 
>   arch/arm64/kernel/topology.c  |  14 -----
>   drivers/base/arch_topology.c  |  92 +++++++++++++++++----------
>   drivers/base/cacheinfo.c      | 114 +++++++++++++++++++++-------------
>   include/linux/arch_topology.h |   1 -
>   include/linux/cacheinfo.h     |   3 +
>   5 files changed, 135 insertions(+), 89 deletions(-)
> 

I tried this series on virtual machine where ACPI is enabled and looks good.
Especially for PATCH[10], resolving the issue I have. So I provided my tested-by
tag for it. Besides, I checked the changes related to ACPI part and looks to
me either after the mentioned nits fixed. I leave the changes related to device-tree
to be reviewed by the experts :)

Thanks,
Gavin