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

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Date:   Wed, 29 Mar 2023 08:41:43 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Yicong Yang <yangyicong@...wei.com>, rafael@...nel.org,
        pierre.gondois@....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 01:47:21PM +0100, Sudeep Holla wrote:
> 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 ?

Will do, thanks!