[Xen-devel] Shouldn't remove device in pci_bus_probe_wrapper()

["Han, Weidong" <weidong.han@xxxxxxxxx>]

Hi,

In pci_bus_probe_wrapper(), it adds (assign) a device to dom0 firstly, but if 
pci_bus_probe() for the device fails (don't have driver), the device will be 
removed (deassigned) from dom0. For PCIe-to-PCI bridges, they are removed from 
dom0 when they are hooked by pci_bus_probe_wrapper(). That's to say they are 
not mapped in VT-d page table. Thus the PCI devices under these bridges cannot 
work. This situation happens when install pciback module, because pciback will 
probe these bridges and removed them from dom0. Built-in pciback won't result 
in this problem due to these bridges (for example 00:1e.0) are probed before 
their devices (for example 02:00.0). (When map a pci device (02:00.0) to VT-d, 
it will also map its pcie-to-pci bridge (00:1e.0) to VT-d)

So I think should not remove (deassign) devices from dom0 when pci_bus_probe() 
fails. Each device which can DMA should be mapped in VT-d when VT-d is enabled. 
But current code make it possible some these devices are not mapped into VT-d.


Following is the patch to don't remove device from dom0 when pci_bus_probe() 
fails.


diff -r 2fb13b8cbe13 drivers/xen/core/pci.c
--- a/drivers/xen/core/pci.c    Thu Oct 30 13:34:43 2008 +0000
+++ b/drivers/xen/core/pci.c    Thu Nov 06 10:15:26 2008 +0800
@@ -23,14 +23,6 @@ static int pci_bus_probe_wrapper(struct 
                return r;
 
        r = pci_bus_probe(dev);
-       if (r) {
-               int ret;
-
-               ret = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_remove,
-                                           &manage_pci);
-               WARN_ON(ret && ret != -ENOSYS);
-       }
-
        return r;
 }
 

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