[PATCH v2 3/3] x86/msi: clear initial MSI-X state on boot

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Some firmware/devices are found to not reset MSI-X properly, leaving
MASKALL set. Xen relies on initial state being both disabled.
Especially, pci_reset_msix_state() assumes if MASKALL is set, it was Xen
setting it due to msix->host_maskall or msix->guest_maskall. Clearing
just MASKALL might be unsafe if ENABLE is set, so clear them both.

Reported-by: Jason Andryuk <jandryuk@xxxxxxxxx>
Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
v2:
 - new patch
---
 xen/drivers/passthrough/msi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/xen/drivers/passthrough/msi.c b/xen/drivers/passthrough/msi.c
index ce1a450f6f4a..60adad47e379 100644
--- a/xen/drivers/passthrough/msi.c
+++ b/xen/drivers/passthrough/msi.c
@@ -48,6 +48,13 @@ int pdev_msi_init(struct pci_dev *pdev)
         ctrl = pci_conf_read16(pdev->sbdf, msix_control_reg(pos));
         msix->nr_entries = msix_table_size(ctrl);
 
+        /*
+         * Clear both ENABLE and MASKALL, pci_reset_msix_state() relies on this
+         * initial state.
+         */
+        ctrl &= ~(PCI_MSIX_FLAGS_ENABLE|PCI_MSIX_FLAGS_MASKALL);
+        pci_conf_write16(pdev->sbdf, msix_control_reg(pos), ctrl);
+
         pdev->msix = msix;
     }
 
-- 
2.39.2