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Subject[PATCH 4.9 57/93] PCI: Dont update VF BARs while VF memory space is enabled
4.9-stable review patch.  If anyone has any objections, please let me know.


From: Bjorn Helgaas <>

[ Upstream commit 546ba9f8f22f71b0202b6ba8967be5cc6dae4e21 ]

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

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 <>
Reviewed-by: Gavin Shan <>
Signed-off-by: Sasha Levin <>
Signed-off-by: Greg Kroah-Hartman <>
drivers/pci/iov.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -566,6 +566,7 @@ void pci_iov_update_resource(struct pci_
struct resource *res = dev->resource + resno;
int vf_bar = resno - PCI_IOV_RESOURCES;
struct pci_bus_region region;
+ u16 cmd;
u32 new;
int reg;

@@ -577,6 +578,13 @@ void pci_iov_update_resource(struct pci_
if (!iov)

+ 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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