[PATCH 5.12 088/127] xen-pciback: redo VF placement in the virtual topology

[Greg Kroah-Hartman]

From: Jan Beulich <jbeulich@xxxxxxxx>

commit 4ba50e7c423c29639878c00573288869aa627068 upstream.

The commit referenced below was incomplete: It merely affected what
would get written to the vdev-<N> xenstore node. The guest would still
find the function at the original function number as long as
__xen_pcibk_get_pci_dev() wouldn't be in sync. The same goes for AER wrt
__xen_pcibk_get_pcifront_dev().

Undo overriding the function to zero and instead make sure that VFs at
function zero remain alone in their slot. This has the added benefit of
improving overall capacity, considering that there's only a total of 32
slots available right now (PCI segment and bus can both only ever be
zero at present).

Fixes: 8a5248fe10b1 ("xen PV passthru: assign SR-IOV virtual functions to separate virtual slots")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Link: https://lore.kernel.org/r/8def783b-404c-3452-196d-3f3fd4d72c9e@xxxxxxxx
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/xen/xen-pciback/vpci.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/drivers/xen/xen-pciback/vpci.c
+++ b/drivers/xen/xen-pciback/vpci.c
@@ -70,7 +70,7 @@ static int __xen_pcibk_add_pci_dev(struc
 				   struct pci_dev *dev, int devid,
 				   publish_pci_dev_cb publish_cb)
 {
-	int err = 0, slot, func = -1;
+	int err = 0, slot, func = PCI_FUNC(dev->devfn);
 	struct pci_dev_entry *t, *dev_entry;
 	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
 
@@ -95,22 +95,25 @@ static int __xen_pcibk_add_pci_dev(struc
 
 	/*
 	 * Keep multi-function devices together on the virtual PCI bus, except
-	 * virtual functions.
+	 * that we want to keep virtual functions at func 0 on their own. They
+	 * aren't multi-function devices and hence their presence at func 0
+	 * may cause guests to not scan the other functions.
 	 */
-	if (!dev->is_virtfn) {
+	if (!dev->is_virtfn || func) {
 		for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
 			if (list_empty(&vpci_dev->dev_list[slot]))
 				continue;
 
 			t = list_entry(list_first(&vpci_dev->dev_list[slot]),
 				       struct pci_dev_entry, list);
+			if (t->dev->is_virtfn && !PCI_FUNC(t->dev->devfn))
+				continue;
 
 			if (match_slot(dev, t->dev)) {
 				dev_info(&dev->dev, "vpci: assign to virtual slot %d func %d\n",
-					 slot, PCI_FUNC(dev->devfn));
+					 slot, func);
 				list_add_tail(&dev_entry->list,
 					      &vpci_dev->dev_list[slot]);
-				func = PCI_FUNC(dev->devfn);
 				goto unlock;
 			}
 		}
@@ -123,7 +126,6 @@ static int __xen_pcibk_add_pci_dev(struc
 				 slot);
 			list_add_tail(&dev_entry->list,
 				      &vpci_dev->dev_list[slot]);
-			func = dev->is_virtfn ? 0 : PCI_FUNC(dev->devfn);
 			goto unlock;
 		}
 	}