[ 38/58] xen/pciback: Restore the PCI config space after an FLR.

From: Greg Kroah-Hartman
Date: Thu Oct 04 2012 - 17:22:06 EST


3.5-stable review patch. If anyone has any objections, please let me know.

------------------

From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

commit c341ca45ce56143804ef5a8f4db753e554e640b4 upstream.

When we do an FLR, or D0->D3_hot we may lose the BARs as the
device has turned itself off (and on). This means the device cannot
function unless the pci_restore_state is called - which it is
when the PCI device is unbound from the Xen PCI backend driver.
For PV guests it ends up calling pci_enable_device / pci_enable_msi[x]
which does the proper steps

That however is not happening if a HVM guest is run as QEMU
deals with PCI configuration space. QEMU also requires that the
device be "parked" under the ownership of a pci-stub driver to
guarantee that the PCI device is not being used. Hence we
follow the same incantation as pci_reset_function does - by
doing an FLR, then restoring the PCI configuration space.

The result of this patch is that when you run lspci, you get
now this:

- Region 0: [virtual] Memory at fe8c0000 (32-bit, non-prefetchable) [size=128K]
- Region 1: [virtual] Memory at fe800000 (32-bit, non-prefetchable) [size=512K]
+ Region 0: Memory at fe8c0000 (32-bit, non-prefetchable) [size=128K]
+ Region 1: Memory at fe800000 (32-bit, non-prefetchable) [size=512K]
Region 2: I/O ports at c000 [size=32]
- Region 3: [virtual] Memory at fe8e0000 (32-bit, non-prefetchable) [size=16K]
+ Region 3: Memory at fe8e0000 (32-bit, non-prefetchable) [size=16K]

The [virtual] means that lspci read those entries from SysFS but when
it read them from the device it got a different value (0xfffffff).

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/xen/xen-pciback/pci_stub.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -362,6 +362,7 @@ static int __devinit pcistub_init_device
else {
dev_dbg(&dev->dev, "reseting (FLR, D3, etc) the device\n");
__pci_reset_function_locked(dev);
+ pci_restore_state(dev);
}
/* Now disable the device (this also ensures some private device
* data is setup before we export)


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