The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4ba50e7c423c29639878c00573288869aa627068 Mon Sep 17 00:00:00 2001

From: Jan Beulich jbeulich@suse.com Date: Tue, 18 May 2021 18:13:42 +0200 Subject: [PATCH] xen-pciback: redo VF placement in the virtual topology

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@suse.com Cc: stable@vger.kernel.org Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Link: https://lore.kernel.org/r/8def783b-404c-3452-196d-3f3fd4d72c9e@suse.com Signed-off-by: Juergen Gross jgross@suse.com

diff --git a/drivers/xen/xen-pciback/vpci.c b/drivers/xen/xen-pciback/vpci.c index 4162d0e7e00d..cc7450f2b2a9 100644 --- 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(struct xen_pcibk_device *pdev, 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(struct xen_pcibk_device *pdev,

/* * 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(struct xen_pcibk_device *pdev, slot); list_add_tail(&dev_entry->list, &vpci_dev->dev_list[slot]); - func = dev->is_virtfn ? 0 : PCI_FUNC(dev->devfn); goto unlock; } }