[PATCH v20 4/4] PCI/MSI: Enable memory decoding before restoring MSI-X messages

[Farhan Ali]

The current MSI-X restoration path assumes the Command register Memory bit
is enabled when writing MSI-X messages. But its possible the last saved and
restored state of device may not have the Memory bit enabled, even if a
device driver later enables Memory bit and MSI-X. Attempting to access
Memory space without Memory bit enabled can lead to Unsupported Request
(UR) from the device. Fix this by enabling Memory bit and restore
it afterwards.

Signed-off-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
---
 drivers/pci/msi/msi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
index 81d24a270a79..46a0d9f68a57 100644
--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -874,6 +874,7 @@ void __pci_restore_msix_state(struct pci_dev *dev)
 {
 	struct msi_desc *entry;
 	bool write_msg;
+	u16 cmd;
 
 	if (!dev->msix_enabled)
 		return;
@@ -882,6 +883,8 @@ void __pci_restore_msix_state(struct pci_dev *dev)
 	pci_intx_for_msi(dev, 0);
 	pci_msix_clear_and_set_ctrl(dev, 0,
 				PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL);
+	pci_read_config_word(dev, PCI_COMMAND, &cmd);
+	pci_write_config_word(dev, PCI_COMMAND, cmd | PCI_COMMAND_MEMORY);
 
 	write_msg = arch_restore_msi_irqs(dev);
 
@@ -893,6 +896,7 @@ void __pci_restore_msix_state(struct pci_dev *dev)
 		}
 	}
 
+	pci_write_config_word(dev, PCI_COMMAND, cmd);
 	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
 }
 
-- 
2.43.0