[2/2] ACPI: HMAT: Fix initiator registration for single-initiator systems

  In a system with a single initiator node, and one or more memory-only
'target' nodes, the memory-only node(s) would fail to register their
initiator node correctly. i.e. in sysfs:

  # ls /sys/devices/system/node/node0/access0/targets/
  node0

Where as the correct behavior should be:

  # ls /sys/devices/system/node/node0/access0/targets/
  node0 node1

This happened because hmat_register_target_initiators() uses list_sort()
to sort the initiator list, but the sort comparision function
(initiator_cmp()) is overloaded to also set the node mask's bits.

In a system with a single initiator, the list is singular, and list_sort
elides the comparision helper call. Thus the node mask never gets set,
and the subsequent search for the best initiator comes up empty.

Add a new helper to sort the initiator list, and handle the singular
list corner case by setting the node mask for that explicitly.

Reported-by: Chris Piper <chris.d.piper@intel.com>
Cc: <stable@vger.kernel.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 drivers/acpi/numa/hmat.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)
  

On Wed, Nov 16, 2022 at 12:57:36AM -0700, Vishal Verma wrote:
> In a system with a single initiator node, and one or more memory-only
> 'target' nodes, the memory-only node(s) would fail to register their
> initiator node correctly. i.e. in sysfs:
> 
>   # ls /sys/devices/system/node/node0/access0/targets/
>   node0
> 
> Where as the correct behavior should be:
> 
>   # ls /sys/devices/system/node/node0/access0/targets/
>   node0 node1
> 
> This happened because hmat_register_target_initiators() uses list_sort()
> to sort the initiator list, but the sort comparision function
> (initiator_cmp()) is overloaded to also set the node mask's bits.
> 
> In a system with a single initiator, the list is singular, and list_sort
> elides the comparision helper call. Thus the node mask never gets set,
> and the subsequent search for the best initiator comes up empty.
> 
> Add a new helper to sort the initiator list, and handle the singular
> list corner case by setting the node mask for that explicitly.
> 
> Reported-by: Chris Piper <chris.d.piper@intel.com>
> Cc: <stable@vger.kernel.org>
> Cc: Rafael J. Wysocki <rafael@kernel.org>
> Cc: Liu Shixin <liushixin2@huawei.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
>  drivers/acpi/numa/hmat.c | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> index 144a84f429ed..cd20b0e9cdfa 100644
> --- a/drivers/acpi/numa/hmat.c
> +++ b/drivers/acpi/numa/hmat.c
> @@ -573,6 +573,30 @@ static int initiator_cmp(void *priv, const struct list_head *a,
>  	return ia->processor_pxm - ib->processor_pxm;
>  }
>  
> +static int initiators_to_nodemask(unsigned long *p_nodes)
> +{
> +	/*
> +	 * list_sort doesn't call @cmp (initiator_cmp) for 0 or 1 sized lists.
> +	 * For a single-initiator system with other memory-only nodes, this
> +	 * means an empty p_nodes mask, since that is set by initiator_cmp().
> +	 * Special case the singular list, and make sure the node mask gets set
> +	 * appropriately.
> +	 */
> +	if (list_empty(&initiators))
> +		return -ENXIO;
> +
> +	if (list_is_singular(&initiators)) {
> +		struct memory_initiator *initiator = list_first_entry(
> +			&initiators, struct memory_initiator, node);
> +
> +		set_bit(initiator->processor_pxm, p_nodes);
> +		return 0;
> +	}
> +
> +	list_sort(p_nodes, &initiators, initiator_cmp);
> +	return 0;
> +}
> +

Hm. I think it indicates that these set_bit()s do not belong to
initiator_cmp().

Maybe remove both set_bit() from the compare helper and walk the list
separately to initialize the node mask? I think it will be easier to
follow.
  

On Wed, 2022-11-16 at 15:46 +0300, Kirill A. Shutemov wrote:
> On Wed, Nov 16, 2022 at 12:57:36AM -0700, Vishal Verma wrote:
> > In a system with a single initiator node, and one or more memory-only
> > 'target' nodes, the memory-only node(s) would fail to register their
> > initiator node correctly. i.e. in sysfs:
> > 
> >   # ls /sys/devices/system/node/node0/access0/targets/
> >   node0
> > 
> > Where as the correct behavior should be:
> > 
> >   # ls /sys/devices/system/node/node0/access0/targets/
> >   node0 node1
> > 
> > This happened because hmat_register_target_initiators() uses list_sort()
> > to sort the initiator list, but the sort comparision function
> > (initiator_cmp()) is overloaded to also set the node mask's bits.
> > 
> > In a system with a single initiator, the list is singular, and list_sort
> > elides the comparision helper call. Thus the node mask never gets set,
> > and the subsequent search for the best initiator comes up empty.
> > 
> > Add a new helper to sort the initiator list, and handle the singular
> > list corner case by setting the node mask for that explicitly.
> > 
> > Reported-by: Chris Piper <chris.d.piper@intel.com>
> > Cc: <stable@vger.kernel.org>
> > Cc: Rafael J. Wysocki <rafael@kernel.org>
> > Cc: Liu Shixin <liushixin2@huawei.com>
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> > ---
> >  drivers/acpi/numa/hmat.c | 32 ++++++++++++++++++++++++++++++--
> >  1 file changed, 30 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> > index 144a84f429ed..cd20b0e9cdfa 100644
> > --- a/drivers/acpi/numa/hmat.c
> > +++ b/drivers/acpi/numa/hmat.c
> > @@ -573,6 +573,30 @@ static int initiator_cmp(void *priv, const struct list_head *a,
> >         return ia->processor_pxm - ib->processor_pxm;
> >  }
> >  
> > +static int initiators_to_nodemask(unsigned long *p_nodes)
> > +{
> > +       /*
> > +        * list_sort doesn't call @cmp (initiator_cmp) for 0 or 1 sized lists.
> > +        * For a single-initiator system with other memory-only nodes, this
> > +        * means an empty p_nodes mask, since that is set by initiator_cmp().
> > +        * Special case the singular list, and make sure the node mask gets set
> > +        * appropriately.
> > +        */
> > +       if (list_empty(&initiators))
> > +               return -ENXIO;
> > +
> > +       if (list_is_singular(&initiators)) {
> > +               struct memory_initiator *initiator = list_first_entry(
> > +                       &initiators, struct memory_initiator, node);
> > +
> > +               set_bit(initiator->processor_pxm, p_nodes);
> > +               return 0;
> > +       }
> > +
> > +       list_sort(p_nodes, &initiators, initiator_cmp);
> > +       return 0;
> > +}
> > +
> 
> Hm. I think it indicates that these set_bit()s do not belong to
> initiator_cmp().
> 
> Maybe remove both set_bit() from the compare helper and walk the list
> separately to initialize the node mask? I think it will be easier to
> follow.


Yes - I thuoght about this, but went with the seemingly less intrusive
change. I can send a v2 which separates out the set_bit()s. I agree
that's cleaner and easier to follow than overloading initiator_cmp().
  

On Wed, Nov 16, 2022 at 06:02:32PM +0000, Verma, Vishal L wrote:
> On Wed, 2022-11-16 at 15:46 +0300, Kirill A. Shutemov wrote:
> > On Wed, Nov 16, 2022 at 12:57:36AM -0700, Vishal Verma wrote:
> > > In a system with a single initiator node, and one or more memory-only
> > > 'target' nodes, the memory-only node(s) would fail to register their
> > > initiator node correctly. i.e. in sysfs:
> > > 
> > >   # ls /sys/devices/system/node/node0/access0/targets/
> > >   node0
> > > 
> > > Where as the correct behavior should be:
> > > 
> > >   # ls /sys/devices/system/node/node0/access0/targets/
> > >   node0 node1
> > > 
> > > This happened because hmat_register_target_initiators() uses list_sort()
> > > to sort the initiator list, but the sort comparision function
> > > (initiator_cmp()) is overloaded to also set the node mask's bits.
> > > 
> > > In a system with a single initiator, the list is singular, and list_sort
> > > elides the comparision helper call. Thus the node mask never gets set,
> > > and the subsequent search for the best initiator comes up empty.
> > > 
> > > Add a new helper to sort the initiator list, and handle the singular
> > > list corner case by setting the node mask for that explicitly.
> > > 
> > > Reported-by: Chris Piper <chris.d.piper@intel.com>
> > > Cc: <stable@vger.kernel.org>
> > > Cc: Rafael J. Wysocki <rafael@kernel.org>
> > > Cc: Liu Shixin <liushixin2@huawei.com>
> > > Cc: Dan Williams <dan.j.williams@intel.com>
> > > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> > > ---
> > >  drivers/acpi/numa/hmat.c | 32 ++++++++++++++++++++++++++++++--
> > >  1 file changed, 30 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> > > index 144a84f429ed..cd20b0e9cdfa 100644
> > > --- a/drivers/acpi/numa/hmat.c
> > > +++ b/drivers/acpi/numa/hmat.c
> > > @@ -573,6 +573,30 @@ static int initiator_cmp(void *priv, const struct list_head *a,
> > >         return ia->processor_pxm - ib->processor_pxm;
> > >  }
> > >  
> > > +static int initiators_to_nodemask(unsigned long *p_nodes)
> > > +{
> > > +       /*
> > > +        * list_sort doesn't call @cmp (initiator_cmp) for 0 or 1 sized lists.
> > > +        * For a single-initiator system with other memory-only nodes, this
> > > +        * means an empty p_nodes mask, since that is set by initiator_cmp().
> > > +        * Special case the singular list, and make sure the node mask gets set
> > > +        * appropriately.
> > > +        */
> > > +       if (list_empty(&initiators))
> > > +               return -ENXIO;
> > > +
> > > +       if (list_is_singular(&initiators)) {
> > > +               struct memory_initiator *initiator = list_first_entry(
> > > +                       &initiators, struct memory_initiator, node);
> > > +
> > > +               set_bit(initiator->processor_pxm, p_nodes);
> > > +               return 0;
> > > +       }
> > > +
> > > +       list_sort(p_nodes, &initiators, initiator_cmp);
> > > +       return 0;
> > > +}
> > > +
> > 
> > Hm. I think it indicates that these set_bit()s do not belong to
> > initiator_cmp().
> > 
> > Maybe remove both set_bit() from the compare helper and walk the list
> > separately to initialize the node mask? I think it will be easier to
> > follow.
> 
> 
> Yes - I thuoght about this, but went with the seemingly less intrusive
> change. I can send a v2 which separates out the set_bit()s. I agree
> that's cleaner and easier to follow than overloading initiator_cmp().

Yes, please make v2.

With current implementation set_bit() can be called multiple times on the
same initiator, depending on placement of the initiator in the list.
It is totally wrong place.