[PATCH 0/2] ACPI: HMAT: fix single-initiator target registrations

[PATCH 0/2] ACPI: HMAT: fix single-initiator target registrations

[Vishal Verma]

Patch 1 is an obvious cleanup found while fixing this problem.

Patch 2 Fixes a bug with initiator registration for single-initiator
systems. More details on this in its commit message.


Vishal Verma (2):
  ACPI: HMAT: remove unnecessary variable initialization
  ACPI: HMAT: Fix initiator registration for single-initiator systems

 drivers/acpi/numa/hmat.c | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)


base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780
-- 
2.38.1

[PATCH 1/2] ACPI: HMAT: remove unnecessary variable initialization

[Vishal Verma]

In hmat_register_target_initiators(), the variable 'best' gets
initialized in the outer per-locality-type for loop. The initialization
just before setting up 'Access 1' targets was unnecessary. Remove it.

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 | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 23f49a2f4d14..144a84f429ed 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -644,7 +644,6 @@ static void hmat_register_target_initiators(struct memory_target *target)
 	/* Access 1 ignores Generic Initiators */
 	bitmap_zero(p_nodes, MAX_NUMNODES);
 	list_sort(p_nodes, &initiators, initiator_cmp);
-	best = 0;
 	for (i = WRITE_LATENCY; i <= READ_BANDWIDTH; i++) {
 		loc = localities_types[i];
 		if (!loc)
-- 
2.38.1

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

[Vishal Verma]

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;
+}
+
 static void hmat_register_target_initiators(struct memory_target *target)
 {
 	static DECLARE_BITMAP(p_nodes, MAX_NUMNODES);
@@ -609,7 +633,9 @@ static void hmat_register_target_initiators(struct memory_target *target)
 	 * initiators.
 	 */
 	bitmap_zero(p_nodes, MAX_NUMNODES);
-	list_sort(p_nodes, &initiators, initiator_cmp);
+	if (initiators_to_nodemask(p_nodes) < 0)
+		return;
+
 	if (!access0done) {
 		for (i = WRITE_LATENCY; i <= READ_BANDWIDTH; i++) {
 			loc = localities_types[i];
@@ -643,7 +669,9 @@ static void hmat_register_target_initiators(struct memory_target *target)
 
 	/* Access 1 ignores Generic Initiators */
 	bitmap_zero(p_nodes, MAX_NUMNODES);
-	list_sort(p_nodes, &initiators, initiator_cmp);
+	if (initiators_to_nodemask(p_nodes) < 0)
+		return;
+
 	for (i = WRITE_LATENCY; i <= READ_BANDWIDTH; i++) {
 		loc = localities_types[i];
 		if (!loc)
-- 
2.38.1

Re: [PATCH 0/2] ACPI: HMAT: fix single-initiator target registrations

[Rafael J. Wysocki]

On Wed, Nov 16, 2022 at 8:57 AM Vishal Verma <vishal.l.verma@intel.com> wrote:
>
> Patch 1 is an obvious cleanup found while fixing this problem.
>
> Patch 2 Fixes a bug with initiator registration for single-initiator
> systems. More details on this in its commit message.
>
>
> Vishal Verma (2):
>   ACPI: HMAT: remove unnecessary variable initialization
>   ACPI: HMAT: Fix initiator registration for single-initiator systems

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

for both and please feel free to ask Dan to take them.

Alternatively, if you want me to apply them, please let me know.

>  drivers/acpi/numa/hmat.c | 33 ++++++++++++++++++++++++++++++---
>  1 file changed, 30 insertions(+), 3 deletions(-)
>
>
> base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780
> --

Re: [PATCH 1/2] ACPI: HMAT: remove unnecessary variable initialization

[Kirill A. Shutemov]

On Wed, Nov 16, 2022 at 12:57:35AM -0700, Vishal Verma wrote:
> In hmat_register_target_initiators(), the variable 'best' gets
> initialized in the outer per-locality-type for loop. The initialization
> just before setting up 'Access 1' targets was unnecessary. Remove it.
> 
> 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>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>


-- 
  Kiryl Shutsemau / Kirill A. Shutemov

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

[Kirill A. Shutemov]

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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

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

[Verma, Vishal L]

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().

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

[kirill]

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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov