diff mbox

Setup disabled bridges even if buses are added.

Message ID 20090402155812.5C9A.27C06F64@necst.nec.co.jp
State Superseded, archived
Headers show

Commit Message

Yuji Shimada April 2, 2009, 7:01 a.m. UTC
This patch setups disabled bridges even if buses have already been
added.

pci_assign_unassigned_resources is called after buses are added.
pci_assign_unassigned_resources calls pci_bus_assign_resources.
pci_bus_assign_resources calls pci_setup_bridge to configure BARs of
bridges.

Currently pci_setup_bridge returns immediately if the bus have already
been added. So pci_assign_unassigned_resources can't configure BARs of
bridge.

The patch fixes the issue.

On logical hot-add, we need to prevent the kernel from re-initializing
bridges that have already been initialized. To achieve this,
pci_setup_bridge returns immediately if the bridge have already been
enabled.

Thanks,
--
Yuji Shimada


Signed-off-by: Yuji Shimada <shimada-yxb@necst.nec.co.jp>


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Comments

Alexander Chiang April 2, 2009, 9:51 p.m. UTC | #1
Hello Yuji-san,

* Yuji Shimada <shimada-yxb@necst.nec.co.jp>:
> This patch setups disabled bridges even if buses have already been
> added.
> 
> pci_assign_unassigned_resources is called after buses are added.
> pci_assign_unassigned_resources calls pci_bus_assign_resources.
> pci_bus_assign_resources calls pci_setup_bridge to configure BARs of
> bridges.
> 
> Currently pci_setup_bridge returns immediately if the bus have already
> been added. So pci_assign_unassigned_resources can't configure BARs of
> bridge.

Ok, I agree with your analysis.

> The patch fixes the issue.
> 
> On logical hot-add, we need to prevent the kernel from re-initializing
> bridges that have already been initialized. To achieve this,
> pci_setup_bridge returns immediately if the bridge have already been
> enabled.
> 
> Thanks,
> --
> Yuji Shimada
> 
> 
> Signed-off-by: Yuji Shimada <shimada-yxb@necst.nec.co.jp>
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 334285a..ab27831 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -144,7 +144,7 @@ static void pci_setup_bridge(struct pci_bus *bus)
>  	struct pci_bus_region region;
>  	u32 l, bu, lu, io_upper16;
>  
> -	if (!pci_is_root_bus(bus) && bus->is_added)
> +	if (bus->self == NULL || atomic_read(&bus->self->enable_cnt) != 0)

Doesn't this mean that we will return early on a non-materialized
root bus (aka, a bus without PCI config space)? There are
definitely some platforms like that.

I think you want:

	if (!pci_is_root_bus(bus) && atomic_read(&bus->self->enable_cnt))

which says:
	- always allow pci_setup_bridge on a root bus (which
	  cannot be logically hot-plugged, so don't have to worry
	  about multiple-initializations)
	- on a p2p bridge, return early if already enabled

A non-root bus will always have a valid ->self, so that pointer
dereference should be safe.

Right?

Thanks.

/ac

>  		return;
>  
>  	dev_info(&bridge->dev, "PCI bridge, secondary bus %04x:%02x\n",
> 
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Yuji Shimada April 3, 2009, 2:10 a.m. UTC | #2
On Thu, 2 Apr 2009 15:51:19 -0600
Alex Chiang <achiang@hp.com> wrote:

> Hello Yuji-san,
> 
> * Yuji Shimada <shimada-yxb@necst.nec.co.jp>:
> > This patch setups disabled bridges even if buses have already been
> > added.
> > 
> > pci_assign_unassigned_resources is called after buses are added.
> > pci_assign_unassigned_resources calls pci_bus_assign_resources.
> > pci_bus_assign_resources calls pci_setup_bridge to configure BARs of
> > bridges.
> > 
> > Currently pci_setup_bridge returns immediately if the bus have already
> > been added. So pci_assign_unassigned_resources can't configure BARs of
> > bridge.
> 
> Ok, I agree with your analysis.
> 
> > The patch fixes the issue.
> > 
> > On logical hot-add, we need to prevent the kernel from re-initializing
> > bridges that have already been initialized. To achieve this,
> > pci_setup_bridge returns immediately if the bridge have already been
> > enabled.
> > 
> > Thanks,
> > --
> > Yuji Shimada
> > 
> > 
> > Signed-off-by: Yuji Shimada <shimada-yxb@necst.nec.co.jp>
> > 
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index 334285a..ab27831 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -144,7 +144,7 @@ static void pci_setup_bridge(struct pci_bus *bus)
> >  	struct pci_bus_region region;
> >  	u32 l, bu, lu, io_upper16;
> >  
> > -	if (!pci_is_root_bus(bus) && bus->is_added)
> > +	if (bus->self == NULL || atomic_read(&bus->self->enable_cnt) != 0)
> 
> Doesn't this mean that we will return early on a non-materialized
> root bus (aka, a bus without PCI config space)? There are
> definitely some platforms like that.

Yes, we will return.
pci_setup_bridge can't setup a root bus, because a root bus does not
have a bridge(bus->self).

I find pci_setup_bridge is not called on a root bus. if
pci_setup_bridge is called on a root bus pci_setup_bridge will access
a NULL pointer. So "bus->self == NULL" is not needed.

> I think you want:
> 
> 	if (!pci_is_root_bus(bus) && atomic_read(&bus->self->enable_cnt))
> 
> which says:
> 	- always allow pci_setup_bridge on a root bus (which
> 	  cannot be logically hot-plugged, so don't have to worry
> 	  about multiple-initializations)

I think pci_setup_bridge should return early on a root bus, because
pci_setup_bridge can't setup a root bus. But we don't need to check
whether a bus is a root bus or not as mentioned above.

> 	- on a p2p bridge, return early if already enabled
> 
> A non-root bus will always have a valid ->self, so that pointer
> dereference should be safe.
> 
> Right?

Yes.
pci_setup_bridge is not called on a root bus, so we can assume ->self
is a valid pointer.

Thanks,
--
Yuji Shimada
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diff mbox

Patch

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 334285a..ab27831 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -144,7 +144,7 @@  static void pci_setup_bridge(struct pci_bus *bus)
 	struct pci_bus_region region;
 	u32 l, bu, lu, io_upper16;
 
-	if (!pci_is_root_bus(bus) && bus->is_added)
+	if (bus->self == NULL || atomic_read(&bus->self->enable_cnt) != 0)
 		return;
 
 	dev_info(&bridge->dev, "PCI bridge, secondary bus %04x:%02x\n",