Re: [PATCH v2 2/2] ACPI/PPTT: Handle architecturally unknown cache types

[Jeremy Linton]

Hi,

On 09/17/2018 05:46 PM, Jeffrey Hugo wrote:
> On 9/17/2018 10:17 AM, Sudeep Holla wrote:
> > On 14/09/18 17:28, Jeffrey Hugo wrote:
> > > The type of a cache might not be specified by architectural 
> > > mechanisms (ie
> > > system registers), but its type might be specified in the PPTT. In this
> > > case, we should populate the type of the cache, rather than leave it
> > > undefined.
> > >
> > > This fixes the issue where the cacheinfo driver will not populate sysfs
> > > for such caches, resulting in the information missing from utilities 
> > > like
> > > lstopo and lscpu, thus degrading the user experience.
> > >
> > > Fixes: 2bd00bcd73e5 (ACPI/PPTT: Add Processor Properties Topology 
> > > Table parsing)
> > > Reported-by: Vijaya Kumar K <vkilari@xxxxxxxxxxxxxx>
> > > Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
> > > ---
> > > Â drivers/acpi/pptt.c | 15 +++++++++++----
> > > Â 1 file changed, 11 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> > > index d1e26cb..bb00ed9 100644
> > > --- a/drivers/acpi/pptt.c
> > > +++ b/drivers/acpi/pptt.c
> > > @@ -402,11 +402,18 @@ static void update_cache_properties(struct 
> > > cacheinfo *this_leaf,
> > > ÂÂÂÂÂÂÂÂÂ }
> > > ÂÂÂÂÂ }
> > > ÂÂÂÂÂ /*
> > > -ÂÂÂÂ * If the above flags are valid, and the cache type is NOCACHE
> > > -ÂÂÂÂ * update the cache type as well.
> > > +ÂÂÂÂ * If cache type is NOCACHE, then the cache hasn't been specified
> > > + * via other mechanisms. Update the type if either the cache has
> > > +ÂÂÂÂ * been fully specified in PPTT, or a cache type has been provided.
> > > +ÂÂÂÂ *
> > > +ÂÂÂÂ * Note, we assume such caches are unified based on conventional 
> > > system
> > > + * design and known examples. Significant work is required 
> > > elsewhere to
> > > +ÂÂÂÂ * fully support data/instruction only type caches which are only
> > > +ÂÂÂÂ * specified in PPTT.
> > > ÂÂÂÂÂÂ */
> > > -ÂÂÂ if (this_leaf->type == CACHE_TYPE_NOCACHE &&
> > > -ÂÂÂÂÂÂÂ valid_flags == PPTT_CHECKED_ATTRIBUTES)
> > > +ÂÂÂ if ((this_leaf->type == CACHE_TYPE_NOCACHE) &&
> > > +ÂÂÂÂÂÂÂ (valid_flags == PPTT_CHECKED_ATTRIBUTES ||
> > > +ÂÂÂÂÂÂÂÂ found_cache->flags & ACPI_PPTT_CACHE_TYPE_VALID))
> > > ÂÂÂÂÂÂÂÂÂ this_leaf->type = CACHE_TYPE_UNIFIED;
> >
> > I thought I did mention that we can drop the valid_flags altogether
> > unless Jeremy has reasons not to.
>
> You suggested that perhaps that could be the case. It seemed like an 
> open question to me. I'm at Linaro Connect without access to the device 
> this week, so I guess someone has roughly a week to chime in that the 
> valid flags should be kept, otherwise I'll try a v3 with them removed.

The point of the valid_flags/CHECKED_ATTRIBUTE was to help assure that a 
minimum set of attributes were being provided by the firmware. If we are 
going to reset the CACHE_TYPE, then we might as well remove the 
valid_flag/CHECKED_ATTRIBUTE counts as it can be easily bypassed.

So, yes please, remove the valid_flags with this change.

Thanks,