On Mon, Nov 28, 2016 at 10:15:21PM -0600, Bjorn Helgaas wrote:
>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@xxxxxxxxxx>
Reviewed-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
>---
> drivers/pci/iov.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
>diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>index d00ed5c..a800ba2 100644
>--- 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
>
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