PCI: Don't update VF BARs while VF memory space is enabled

If we update a VF BAR while it's enabled, there are two potential problems:

  1) Any driver that's using the VF has a cached BAR value that is stale
     after the update, and

  2) We can't update 64-bit BARs atomically, so the intermediate state
     (new lower dword with old upper dword) may conflict with another
     device, and an access by a driver unrelated to the VF may cause a bus
     error.

Warn about attempts to update VF BARs while they are enabled.  This is a
programming error, so use dev_WARN() to get a backtrace.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index aa49954..2480b38 100644 (file)
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -584,6 +584,7 @@ void pci_iov_update_resource(struct pci_dev *dev, int resno)
        struct resource *res = dev->resource + resno;
        int vf_bar = resno - PCI_IOV_RESOURCES;
        struct pci_bus_region region;
+       u16 cmd;
        u32 new;
        int reg;
 
@@ -595,6 +596,13 @@ void pci_iov_update_resource(struct pci_dev *dev, int resno)
        if (!iov)
                return;
 
+       pci_read_config_word(dev, iov->pos + PCI_SRIOV_CTRL, &cmd);
+       if ((cmd & PCI_SRIOV_CTRL_VFE) && (cmd & PCI_SRIOV_CTRL_MSE)) {
+               dev_WARN(&dev->dev, "can't update enabled VF BAR%d %pR\n",
+                        vf_bar, res);
+               return;
+       }
+
        /*
         * Ignore unimplemented BARs, unused resource slots for 64-bit
         * BARs, and non-movable resources, e.g., those described via