[added,to,the,4.1,stable,tree] PCI: Don't update VF BARs while VF memory space is enabled

Message ID 20180118205908.3220-77-alexander.levin@microsoft.com
State New
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  • [added,to,the,4.1,stable,tree] PCI: Don't update VF BARs while VF memory space is enabled
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Commit Message

Sasha Levin Jan. 18, 2018, 9 p.m.
From: Sumit Semwal <sumit.semwal@linaro.org>

This patch has been added to the  stable tree. If you have any
objections, please let us know.




[ 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 <bhelgaas@google.com>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
 drivers/pci/iov.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 06959425cdea..846d4f604ebd 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -564,6 +564,7 @@  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;
@@ -575,6 +576,13 @@  void pci_iov_update_resource(struct pci_dev *dev, int resno)
 	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