From 231c7a57d19304beb0931e6cbe3a4929daf49747 Mon Sep 17 00:00:00 2001 From: Farhan Ali Date: Wed, 5 Aug 2026 09:55:18 -0700 Subject: [PATCH] PCI/MSI: Enable memory decoding before restoring MSI-X messages The current MSI-X restoration path assumes the Command register Memory bit is enabled when writing MSI-X messages. But it's possible the last saved and restored state of a 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. Fixes: 41017f0cac92 ("[PATCH] PCI: MSI(X) save/restore for suspend/resume") Signed-off-by: Farhan Ali [bhelgaas: comment] Signed-off-by: Bjorn Helgaas Reviewed-by: Thomas Gleixner Reviewed-by: Niklas Schnelle Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260805165518.794-6-alifm@linux.ibm.com --- drivers/pci/msi/msi.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c index 209373c92e9e..80a9db417dc8 100644 --- a/drivers/pci/msi/msi.c +++ b/drivers/pci/msi/msi.c @@ -870,6 +870,7 @@ void __pci_restore_msix_state(struct pci_dev *dev) { struct msi_desc *entry; bool write_msg; + u16 cmd; if (!dev->msix_enabled) return; @@ -879,6 +880,14 @@ void __pci_restore_msix_state(struct pci_dev *dev) pci_msix_clear_and_set_ctrl(dev, 0, PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL); + /* + * The restored device state may not have Memory Space enabled. + * Since the MSI-X Table and PBA are in Memory Space, enable it + * while restoring them. + */ + 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); scoped_guard (msi_descs_lock, &dev->dev) { @@ -889,6 +898,7 @@ 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); }