On Fri, Mar 13, 2015 at 09:26:08AM -0500, Bjorn Helgaas wrote:

On Fri, Mar 13, 2015 at 9:01 AM, Konrad Rzeszutek Wilk
[off-list ref] wrote:

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On Fri, Mar 13, 2015 at 08:24:58AM -0500, Bjorn Helgaas wrote:

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On Thu, Mar 12, 2015 at 9:36 PM, Yijing Wang [off-list ref] wrote:

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+  pci_add_resource(&resources, &ioport_resource);
+  pci_add_resource(&resources, &iomem_resource);
+  pci_add_resource(&resources, &busn_resource);

Since I don't want to export busn_resource, you might have to allocate your
own struct resource for it here.  And, of course, figure out the details of
which PCI domain you're in and whether you need to share one struct
resource across several host bridges in the same domain.

Allocate its own resource here is ok for me, as I mentioned in previous reply,
so do we still need to add additional info to figure out which domain own the bus resource ?

That's up to the caller.  Only the platform knows which bridges it wants to
have in the same domain.  In principle, every host bridge could be in its
own domain, since each bridge is the root of a unique PCI hierarchy.  But
some platforms have firmware that assumes otherwise.  I have no idea what
xen assumes.

I'm not xen guy, so I don't know much about it, but because it call pci_scan_bus_parented()
before, and in which busn_resource is always shared for different host bridges(same domain or not),
I think add a static bus resource(0,255) should be safe, at least, it would not introduce new risk.

Something like:

diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index b1ffebe..a69e529 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c

@@ -446,9 +446,15 @@ static int pcifront_scan_root(struct pcifront_device *pdev,
                                 unsigned int domain, unsigned int bus)
 {
        struct pci_bus *b;
+       LIST_HEAD(resources);
        struct pcifront_sd *sd = NULL;
        struct pci_bus_entry *bus_entry = NULL;
        int err = 0;
+       static struct resource busn_res = {
+               .start = 0,
+               .end = 255,
+               .flags = IORESOURCE_BUS,
+       };

 #ifndef CONFIG_PCI_DOMAINS
        if (domain != 0) {

@@ -470,17 +476,21 @@ static int pcifront_scan_root(struct pcifront_device *pdev,
                err = -ENOMEM;
                goto err_out;
        }
+       pci_add_resource(&resources, &ioport_resource);
+       pci_add_resource(&resources, &iomem_resource);
+       pci_add_resource(&resources, &busn_res);
        pcifront_init_sd(sd, domain, bus, pdev);

        pci_lock_rescan_remove();

-       b = pci_scan_bus_parented(&pdev->xdev->dev, bus,
-                                 &pcifront_bus_ops, sd);
+       b = pci_scan_root_bus(&pdev->xdev->dev, bus,
+                                 &pcifront_bus_ops, sd, &resources);
        if (!b) {

Bjorn, what do you think about ?

That seems OK to me.  Probably still wrong, but no worse than it was before.

Interesting. The mechanism for PCI passthrough can either synthesize
and PCI bus number starting at zero (so first device is always 0:0:0.0)
or it can replicate the backend PCI topology. That means you
could have segment values passed in, so: ab:ff:00.1). I've to admin
I hadn't tried the 'physical' replication on an machine with
domains (err, segments).

Is there an git tree with this so I can just try it out?

git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git
pci/enumeration-yw6 has similar code (it exports the single

I presume now it is bjorn/pci/enumeration-yw8 ? Going to test this out
this week.

busn_resource and makes xen use it).  That should be functionally
identical to what v4.0-rc1 does.

Yijing hasn't posted the static busn_res proposal above yet, so I
don't have a branch with that in it.

Bjorn