[Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[David Hildenbrand]

While looking at the s390x implementation, looks like spapr has a
similar BUG when building the topology.

The primary bus number corresponds always to the bus number of the
bus the bridge is attached to.

Right now, if we have two bridges attached to the same bus (e.g. root
bus) this is however not the case. The first bridge will have primary
bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.

While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
Setting it temporarily to that value (as discussed e.g. in [1]), is
only relevant for a running system that probes the buses. The value is
effectively unused for us just doing a DFS.

[1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html

Note: Is hotplug of bridges supported? I can't find where the topology
is fixed up when hotplugging a PCI bridge. (e.g. bus numbers assigned
and PCI_SUBORDINATE_BUS of path to the root updated). But maybe we are
excluding bridges or this is not necessary for some reason.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/ppc/spapr_pci.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index b74f2632ec..5cdc98513d 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -2030,8 +2030,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
                                            void *opaque)
 {
     unsigned int *bus_no = opaque;
-    unsigned int primary = *bus_no;
-    unsigned int subordinate = 0xff;
     PCIBus *sec_bus = NULL;
 
     if ((pci_default_read_config(pdev, PCI_HEADER_TYPE, 1) !=
@@ -2040,7 +2038,7 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
     }
 
     (*bus_no)++;
-    pci_default_write_config(pdev, PCI_PRIMARY_BUS, primary, 1);
+    pci_default_write_config(pdev, PCI_PRIMARY_BUS, pci_dev_bus_num(pdev), 1);
     pci_default_write_config(pdev, PCI_SECONDARY_BUS, *bus_no, 1);
     pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
 
@@ -2049,7 +2047,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
         return;
     }
 
-    pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, subordinate, 1);
     pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
                         spapr_phb_pci_enumerate_bridge, bus_no);
     pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
-- 
2.17.2

Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[David Hildenbrand]

On 23.01.19 09:24, David Hildenbrand wrote:
> While looking at the s390x implementation, looks like spapr has a
> similar BUG when building the topology.
> 
> The primary bus number corresponds always to the bus number of the
> bus the bridge is attached to.
> 
> Right now, if we have two bridges attached to the same bus (e.g. root
> bus) this is however not the case. The first bridge will have primary
> bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.
> 
> While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
> Setting it temporarily to that value (as discussed e.g. in [1]), is
> only relevant for a running system that probes the buses. The value is
> effectively unused for us just doing a DFS.
> 
> [1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html
> 
> Note: Is hotplug of bridges supported? I can't find where the topology
> is fixed up when hotplugging a PCI bridge. (e.g. bus numbers assigned
> and PCI_SUBORDINATE_BUS of path to the root updated). But maybe we are
> excluding bridges or this is not necessary for some reason.

This note can be dropped. I learned that this is under guest control.
(which has to reserve bus numbers and rebuild the topology)

> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/ppc/spapr_pci.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index b74f2632ec..5cdc98513d 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -2030,8 +2030,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
>                                             void *opaque)
>  {
>      unsigned int *bus_no = opaque;
> -    unsigned int primary = *bus_no;
> -    unsigned int subordinate = 0xff;
>      PCIBus *sec_bus = NULL;
>  
>      if ((pci_default_read_config(pdev, PCI_HEADER_TYPE, 1) !=
> @@ -2040,7 +2038,7 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
>      }
>  
>      (*bus_no)++;
> -    pci_default_write_config(pdev, PCI_PRIMARY_BUS, primary, 1);
> +    pci_default_write_config(pdev, PCI_PRIMARY_BUS, pci_dev_bus_num(pdev), 1);
>      pci_default_write_config(pdev, PCI_SECONDARY_BUS, *bus_no, 1);
>      pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
>  
> @@ -2049,7 +2047,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
>          return;
>      }
>  
> -    pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, subordinate, 1);
>      pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
>                          spapr_phb_pci_enumerate_bridge, bus_no);
>      pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
> 


-- 

Thanks,

David / dhildenb

Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[Alexey Kardashevskiy]

On 23/01/2019 19:24, David Hildenbrand wrote:
> While looking at the s390x implementation, looks like spapr has a
> similar BUG when building the topology.
> 
> The primary bus number corresponds always to the bus number of the
> bus the bridge is attached to.
> 
> Right now, if we have two bridges attached to the same bus (e.g. root
> bus) this is however not the case. The first bridge will have primary
> bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.
> 
> While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
> Setting it temporarily to that value (as discussed e.g. in [1]), is
> only relevant for a running system that probes the buses. The value is
> effectively unused for us just doing a DFS.

What is DFS?

> 
> [1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html
> 
> Note: Is hotplug of bridges supported? I can't find where the topology
> is fixed up when hotplugging a PCI bridge. (e.g. bus numbers assigned
> and PCI_SUBORDINATE_BUS of path to the root updated). But maybe we are
> excluding bridges or this is not necessary for some reason.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>


Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>


> ---
>  hw/ppc/spapr_pci.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index b74f2632ec..5cdc98513d 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -2030,8 +2030,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
>                                             void *opaque)
>  {
>      unsigned int *bus_no = opaque;
> -    unsigned int primary = *bus_no;
> -    unsigned int subordinate = 0xff;
>      PCIBus *sec_bus = NULL;
>  
>      if ((pci_default_read_config(pdev, PCI_HEADER_TYPE, 1) !=
> @@ -2040,7 +2038,7 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
>      }
>  
>      (*bus_no)++;
> -    pci_default_write_config(pdev, PCI_PRIMARY_BUS, primary, 1);
> +    pci_default_write_config(pdev, PCI_PRIMARY_BUS, pci_dev_bus_num(pdev), 1);
>      pci_default_write_config(pdev, PCI_SECONDARY_BUS, *bus_no, 1);
>      pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
>  
> @@ -2049,7 +2047,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
>          return;
>      }
>  
> -    pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, subordinate, 1);
>      pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
>                          spapr_phb_pci_enumerate_bridge, bus_no);
>      pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
> 

-- 
Alexey

Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[David Hildenbrand]

On 24.01.19 03:48, Alexey Kardashevskiy wrote:
> 
> 
> On 23/01/2019 19:24, David Hildenbrand wrote:
>> While looking at the s390x implementation, looks like spapr has a
>> similar BUG when building the topology.
>>
>> The primary bus number corresponds always to the bus number of the
>> bus the bridge is attached to.
>>
>> Right now, if we have two bridges attached to the same bus (e.g. root
>> bus) this is however not the case. The first bridge will have primary
>> bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.
>>
>> While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
>> Setting it temporarily to that value (as discussed e.g. in [1]), is
>> only relevant for a running system that probes the buses. The value is
>> effectively unused for us just doing a DFS.
> 
> What is DFS?

Depth-first search :)

> 
>>
>> [1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html
>>
>> Note: Is hotplug of bridges supported? I can't find where the topology
>> is fixed up when hotplugging a PCI bridge. (e.g. bus numbers assigned
>> and PCI_SUBORDINATE_BUS of path to the root updated). But maybe we are
>> excluding bridges or this is not necessary for some reason.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> 
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> 
> 

Thanks!


-- 

Thanks,

David / dhildenb

Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[David Gibson]

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On Thu, Jan 24, 2019 at 01:48:36PM +1100, Alexey Kardashevskiy wrote:
> 
> 
> On 23/01/2019 19:24, David Hildenbrand wrote:
> > While looking at the s390x implementation, looks like spapr has a
> > similar BUG when building the topology.
> > 
> > The primary bus number corresponds always to the bus number of the
> > bus the bridge is attached to.
> > 
> > Right now, if we have two bridges attached to the same bus (e.g. root
> > bus) this is however not the case. The first bridge will have primary
> > bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.
> > 
> > While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
> > Setting it temporarily to that value (as discussed e.g. in [1]), is
> > only relevant for a running system that probes the buses. The value is
> > effectively unused for us just doing a DFS.
> 
> What is DFS?
> 
> > 
> > [1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html
> > 
> > Note: Is hotplug of bridges supported? I can't find where the topology
> > is fixed up when hotplugging a PCI bridge. (e.g. bus numbers assigned
> > and PCI_SUBORDINATE_BUS of path to the root updated). But maybe we are
> > excluding bridges or this is not necessary for some reason.
> > 
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> 
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Applied, thanks.

> 
> 
> > ---
> >  hw/ppc/spapr_pci.c | 5 +----
> >  1 file changed, 1 insertion(+), 4 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index b74f2632ec..5cdc98513d 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -2030,8 +2030,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
> >                                             void *opaque)
> >  {
> >      unsigned int *bus_no = opaque;
> > -    unsigned int primary = *bus_no;
> > -    unsigned int subordinate = 0xff;
> >      PCIBus *sec_bus = NULL;
> >  
> >      if ((pci_default_read_config(pdev, PCI_HEADER_TYPE, 1) !=
> > @@ -2040,7 +2038,7 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
> >      }
> >  
> >      (*bus_no)++;
> > -    pci_default_write_config(pdev, PCI_PRIMARY_BUS, primary, 1);
> > +    pci_default_write_config(pdev, PCI_PRIMARY_BUS, pci_dev_bus_num(pdev), 1);
> >      pci_default_write_config(pdev, PCI_SECONDARY_BUS, *bus_no, 1);
> >      pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
> >  
> > @@ -2049,7 +2047,6 @@ static void spapr_phb_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
> >          return;
> >      }
> >  
> > -    pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, subordinate, 1);
> >      pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
> >                          spapr_phb_pci_enumerate_bridge, bus_no);
> >      pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, *bus_no, 1);
> > 
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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