[PATCH v9 4/4] PCI: Allow extend_bridge_window() to shrink resource if necessary

[PATCH v9 4/4] PCI: Allow extend_bridge_window() to shrink resource if necessary

[Nicholas Johnson]

Remove checks for resource size in extend_bridge_window(). This is
necessary to allow the pci_bus_distribute_available_resources() to
function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
allocate resources. Because the kernel parameter sets the size of all
hotplug bridges to be the same, there are problems when nested hotplug
bridges are encountered. Fitting a downstream hotplug bridge with size X
and normal bridges with non-zero size Y into parent hotplug bridge with
size X is impossible, and hence the downstream hotplug bridge needs to
shrink to fit into its parent.

Add check for if bridge is extended or shrunken and adjust pci_dbg to
reflect this.

Reset the resource if its new size is zero (if we have run out of a
bridge window resource) to prevent the PCI resource assignment code from
attempting to assign a zero-sized resource.

Rename extend_bridge_window() to adjust_bridge_window() to reflect the
fact that the window can now shrink.

Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
---
 drivers/pci/setup-bus.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index fe8b2c715..f8cd54584 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1814,7 +1814,7 @@ void __init pci_assign_unassigned_resources(void)
 	}
 }
 
-static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
+static void adjust_bridge_window(struct pci_dev *bridge, struct resource *res,
 				 struct list_head *add_list,
 				 resource_size_t new_size)
 {
@@ -1823,13 +1823,20 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
 	if (res->parent)
 		return;
 
-	if (resource_size(res) >= new_size)
-		return;
+	if (new_size > resource_size(res)) {
+		add_size = new_size - resource_size(res);
+		pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
+			&add_size);
+	} else if (new_size < resource_size(res)) {
+		add_size = resource_size(res) - new_size;
+		pci_dbg(bridge, "bridge window %pR shrunken by %pa\n", res,
+			&add_size);
+	}
 
-	add_size = new_size - resource_size(res);
-	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
 	res->end = res->start + new_size - 1;
 	remove_from_list(add_list, res);
+	if (!new_size)
+		reset_resource(res);
 }
 
 static void pci_bus_distribute_available_resources(struct pci_bus *bus,
@@ -1865,9 +1872,9 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
 	 * Update the resources to fill as much remaining resource space in the
 	 * parent bridge as possible, while considering alignment.
 	 */
-	extend_bridge_window(bridge, io_res, add_list, resource_size(&io));
-	extend_bridge_window(bridge, mmio_res, add_list, resource_size(&mmio));
-	extend_bridge_window(bridge, mmio_pref_res, add_list,
+	adjust_bridge_window(bridge, io_res, add_list, resource_size(&io));
+	adjust_bridge_window(bridge, mmio_res, add_list, resource_size(&mmio));
+	adjust_bridge_window(bridge, mmio_pref_res, add_list,
 			     resource_size(&mmio_pref));
 
 	/*
-- 
2.23.0

Re: [PATCH v9 4/4] PCI: Allow extend_bridge_window() to shrink resource if necessary

[mika.westerberg]

On Tue, Oct 29, 2019 at 03:29:21PM +0000, Nicholas Johnson wrote:
> Remove checks for resource size in extend_bridge_window(). This is
> necessary to allow the pci_bus_distribute_available_resources() to
> function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
> allocate resources. Because the kernel parameter sets the size of all
> hotplug bridges to be the same, there are problems when nested hotplug
> bridges are encountered. Fitting a downstream hotplug bridge with size X
> and normal bridges with non-zero size Y into parent hotplug bridge with
> size X is impossible, and hence the downstream hotplug bridge needs to
> shrink to fit into its parent.
> 
> Add check for if bridge is extended or shrunken and adjust pci_dbg to
> reflect this.
> 
> Reset the resource if its new size is zero (if we have run out of a
> bridge window resource) to prevent the PCI resource assignment code from
> attempting to assign a zero-sized resource.
> 
> Rename extend_bridge_window() to adjust_bridge_window() to reflect the
> fact that the window can now shrink.
> 
> Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
> ---
>  drivers/pci/setup-bus.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index fe8b2c715..f8cd54584 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1814,7 +1814,7 @@ void __init pci_assign_unassigned_resources(void)
>  	}
>  }
>  
> -static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
> +static void adjust_bridge_window(struct pci_dev *bridge, struct resource *res,
>  				 struct list_head *add_list,
>  				 resource_size_t new_size)
>  {
> @@ -1823,13 +1823,20 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
>  	if (res->parent)
>  		return;
>  
> -	if (resource_size(res) >= new_size)
> -		return;
> +	if (new_size > resource_size(res)) {
> +		add_size = new_size - resource_size(res);
> +		pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
> +			&add_size);
> +	} else if (new_size < resource_size(res)) {
> +		add_size = resource_size(res) - new_size;
> +		pci_dbg(bridge, "bridge window %pR shrunken by %pa\n", res,
> +			&add_size);
> +	}

Do we need to care about new_size == resource_size(res)?

Also there are several calls of resource_size(res) above so probably
worth storing it into a helper variable.

> -	add_size = new_size - resource_size(res);
> -	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
>  	res->end = res->start + new_size - 1;
>  	remove_from_list(add_list, res);
> +	if (!new_size)
> +		reset_resource(res);
>  }

Re: [PATCH v9 4/4] PCI: Allow extend_bridge_window() to shrink resource if necessary

[Nicholas Johnson]

On Wed, Oct 30, 2019 at 02:07:05PM +0200, mika.westerberg@linux.intel.com wrote:
> On Tue, Oct 29, 2019 at 03:29:21PM +0000, Nicholas Johnson wrote:
> > Remove checks for resource size in extend_bridge_window(). This is
> > necessary to allow the pci_bus_distribute_available_resources() to
> > function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
> > allocate resources. Because the kernel parameter sets the size of all
> > hotplug bridges to be the same, there are problems when nested hotplug
> > bridges are encountered. Fitting a downstream hotplug bridge with size X
> > and normal bridges with non-zero size Y into parent hotplug bridge with
> > size X is impossible, and hence the downstream hotplug bridge needs to
> > shrink to fit into its parent.
> > 
> > Add check for if bridge is extended or shrunken and adjust pci_dbg to
> > reflect this.
> > 
> > Reset the resource if its new size is zero (if we have run out of a
> > bridge window resource) to prevent the PCI resource assignment code from
> > attempting to assign a zero-sized resource.
> > 
> > Rename extend_bridge_window() to adjust_bridge_window() to reflect the
> > fact that the window can now shrink.
> > 
> > Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
> > ---
> >  drivers/pci/setup-bus.c | 23 +++++++++++++++--------
> >  1 file changed, 15 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index fe8b2c715..f8cd54584 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -1814,7 +1814,7 @@ void __init pci_assign_unassigned_resources(void)
> >  	}
> >  }
> >  
> > -static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
> > +static void adjust_bridge_window(struct pci_dev *bridge, struct resource *res,
> >  				 struct list_head *add_list,
> >  				 resource_size_t new_size)
> >  {
> > @@ -1823,13 +1823,20 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
> >  	if (res->parent)
> >  		return;
> >  
> > -	if (resource_size(res) >= new_size)
> > -		return;
> > +	if (new_size > resource_size(res)) {
> > +		add_size = new_size - resource_size(res);
> > +		pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
> > +			&add_size);
> > +	} else if (new_size < resource_size(res)) {
> > +		add_size = resource_size(res) - new_size;
> > +		pci_dbg(bridge, "bridge window %pR shrunken by %pa\n", res,
> > +			&add_size);
> > +	}
> 
> Do we need to care about new_size == resource_size(res)?
Sorry, I skipped over this before re-posting. If we are not changing the 
size, does it need to be logged in pci_dbg? I could change it to ">=", 
meaning if the size does not change then it will be "extended" by 0 in 
pci_dbg.

Let me know if you wish for this to happen. But I am easy either way.

If you are fine with how it is, PATCH v10 should have addressed 
everything so far.
> 
> Also there are several calls of resource_size(res) above so probably
> worth storing it into a helper variable.
> 
> > -	add_size = new_size - resource_size(res);
> > -	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
> >  	res->end = res->start + new_size - 1;
> >  	remove_from_list(add_list, res);
> > +	if (!new_size)
> > +		reset_resource(res);
> >  }
Cheers

Re: [PATCH v9 4/4] PCI: Allow extend_bridge_window() to shrink resource if necessary

[mika.westerberg]

On Wed, Oct 30, 2019 at 01:22:44PM +0000, Nicholas Johnson wrote:
> On Wed, Oct 30, 2019 at 02:07:05PM +0200, mika.westerberg@linux.intel.com wrote:
> > On Tue, Oct 29, 2019 at 03:29:21PM +0000, Nicholas Johnson wrote:
> > > Remove checks for resource size in extend_bridge_window(). This is
> > > necessary to allow the pci_bus_distribute_available_resources() to
> > > function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
> > > allocate resources. Because the kernel parameter sets the size of all
> > > hotplug bridges to be the same, there are problems when nested hotplug
> > > bridges are encountered. Fitting a downstream hotplug bridge with size X
> > > and normal bridges with non-zero size Y into parent hotplug bridge with
> > > size X is impossible, and hence the downstream hotplug bridge needs to
> > > shrink to fit into its parent.
> > > 
> > > Add check for if bridge is extended or shrunken and adjust pci_dbg to
> > > reflect this.
> > > 
> > > Reset the resource if its new size is zero (if we have run out of a
> > > bridge window resource) to prevent the PCI resource assignment code from
> > > attempting to assign a zero-sized resource.
> > > 
> > > Rename extend_bridge_window() to adjust_bridge_window() to reflect the
> > > fact that the window can now shrink.
> > > 
> > > Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
> > > ---
> > >  drivers/pci/setup-bus.c | 23 +++++++++++++++--------
> > >  1 file changed, 15 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > > index fe8b2c715..f8cd54584 100644
> > > --- a/drivers/pci/setup-bus.c
> > > +++ b/drivers/pci/setup-bus.c
> > > @@ -1814,7 +1814,7 @@ void __init pci_assign_unassigned_resources(void)
> > >  	}
> > >  }
> > >  
> > > -static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
> > > +static void adjust_bridge_window(struct pci_dev *bridge, struct resource *res,
> > >  				 struct list_head *add_list,
> > >  				 resource_size_t new_size)
> > >  {
> > > @@ -1823,13 +1823,20 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
> > >  	if (res->parent)
> > >  		return;
> > >  
> > > -	if (resource_size(res) >= new_size)
> > > -		return;
> > > +	if (new_size > resource_size(res)) {
> > > +		add_size = new_size - resource_size(res);
> > > +		pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
> > > +			&add_size);
> > > +	} else if (new_size < resource_size(res)) {
> > > +		add_size = resource_size(res) - new_size;
> > > +		pci_dbg(bridge, "bridge window %pR shrunken by %pa\n", res,
> > > +			&add_size);
> > > +	}
> > 
> > Do we need to care about new_size == resource_size(res)?
> Sorry, I skipped over this before re-posting. If we are not changing the 
> size, does it need to be logged in pci_dbg? I could change it to ">=", 
> meaning if the size does not change then it will be "extended" by 0 in 
> pci_dbg.
> 
> Let me know if you wish for this to happen. But I am easy either way.

No need.

> If you are fine with how it is, PATCH v10 should have addressed 
> everything so far.

Yes, v10 looks fine by me.