[PATCH v19 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 if we write MSI-X
messages, and restore it afterwards.

Signed-off-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
---
 drivers/pci/msi/msi.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
index 81d24a270a79..d8d3c8a911ac 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;
@@ -884,6 +885,11 @@ void __pci_restore_msix_state(struct pci_dev *dev)
 				PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL);
 
 	write_msg = arch_restore_msi_irqs(dev);
+	if (write_msg) {
+		pci_read_config_word(dev, PCI_COMMAND, &cmd);
+		pci_write_config_word(dev, PCI_COMMAND,
+				      cmd | PCI_COMMAND_MEMORY);
+	}
 
 	scoped_guard (msi_descs_lock, &dev->dev) {
 		msi_for_each_desc(entry, &dev->dev, MSI_DESC_ALL) {
@@ -893,6 +899,9 @@ void __pci_restore_msix_state(struct pci_dev *dev)
 		}
 	}
 
+	if (write_msg)
+		pci_write_config_word(dev, PCI_COMMAND, cmd);
+
 	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
 }
 
-- 
2.43.0