linux-kernel - Re: [PATCH v2] cacheinfo: Fix LLC is not exported through sysfs

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Date:   Tue, 28 Mar 2023 13:47:21 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Yicong Yang <yangyicong@...wei.com>, gregkh@...uxfoundation.org
Cc:     rafael@...nel.org, pierre.gondois@....com,
        Sudeep Holla <sudeep.holla@....com>, palmer@...osinc.com,
        linux-kernel@...r.kernel.org, prime.zeng@...ilicon.com,
        linuxarm@...wei.com, yangyicong@...ilicon.com
Subject: Re: [PATCH v2] cacheinfo: Fix LLC is not exported through sysfs

On Tue, Mar 28, 2023 at 07:49:15PM +0800, Yicong Yang wrote:
> From: Yicong Yang <yangyicong@...ilicon.com>
> 
> After entering 6.3-rc1 the LLC cacheinfo is not exported on our ACPI

I would have preferred the commit causing the issue as you know and have
it in the fixes tag, but info is there so I don't think it is worth another
version churn. Sorry my bad for missing it earlier.

> based arm64 server. This is because the LLC cacheinfo is partly reset
> when secondary CPUs boot up. On arm64 the primary cpu will allocate
> and setup cacheinfo:
> init_cpu_topology()
>   for_each_possible_cpu()
>     fetch_cache_info() // Allocate cacheinfo and init levels
> detect_cache_attributes()
>   cache_shared_cpu_map_setup()
>     if (!last_level_cache_is_valid()) // not valid, setup LLC
>       cache_setup_properties() // setup LLC
> 
> On secondary CPU boot up:
> detect_cache_attributes()
>   populate_cache_leaves()
>     get_cache_type() // Get cache type from clidr_el1,
>                      // for LLC type=CACHE_TYPE_NOCACHE
>   cache_shared_cpu_map_setup()
>     if (!last_level_cache_is_valid()) // Valid and won't go to this branch,
>                                       // leave LLC's type=CACHE_TYPE_NOCACHE
> 
> The last_level_cache_is_valid() use cacheinfo->{attributes, fw_token} to
> test it's valid or not, but populate_cache_leaves() will only reset
> LLC's type, so we won't try to re-setup LLC's type and leave it
> CACHE_TYPE_NOCACHE and won't export it through sysfs.
> 
> This patch tries to fix this by not re-populating the cache leaves if
> the LLC is valid.
>

Reviewed-by: Sudeep Holla <sudeep.holla@....com>

Hi Greg,

Can you pick this up in your next round of fixes for v6.3 please ?

--
Regards,
Sudeep