[PATCH v3 3/3] PCI/MSI: Set device flag indicating only 32-bit MSI support

[Bjorn Helgaas]

From: Vidya Sagar <vidyas@xxxxxxxxxx>

The MSI-X Capability requires devices to support 64-bit Message Addresses,
but the MSI Capability can support either 32- or 64-bit addresses.

Previously, we set dev->no_64bit_msi for a few broken devices that
advertise 64-bit MSI support but don't correctly support it.

In addition, check the MSI "64-bit Address Capable" bit for all devices and
set dev->no_64bit_msi for devices that don't advertise 64-bit support.
This allows msi_verify_entries() to catch arch code defects that assign
64-bit addresses when they're not supported.

[bhelgaas: set no_64bit_msi in pci_msi_init(), commit log]
Link: https://lore.kernel.org/r/20201124105035.24573-1-vidyas@xxxxxxxxxx
Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
 drivers/pci/msi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 3e302ca8a96f..29baa81e7be9 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -623,11 +623,11 @@ static int msi_verify_entries(struct pci_dev *dev)
 	struct msi_desc *entry;
 
 	for_each_pci_msi_entry(entry, dev) {
-		if (!dev->no_64bit_msi || !entry->msg.address_hi)
-			continue;
-		pci_err(dev, "Device has broken 64-bit MSI but arch"
-			" tried to assign one above 4G\n");
-		return -EIO;
+		if (entry->msg.address_hi && dev->no_64bit_msi) {
+			pci_err(dev, "arch assigned 64-bit MSI address %#x%08x but device only supports 32 bits\n",
+				entry->msg.address_hi, entry->msg.address_lo);
+			return -EIO;
+		}
 	}
 	return 0;
 }
@@ -1619,6 +1619,9 @@ void pci_msi_init(struct pci_dev *dev)
 	if (ctrl & PCI_MSI_FLAGS_ENABLE)
 		pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS,
 				      ctrl & ~PCI_MSI_FLAGS_ENABLE);
+
+	if (!(ctrl & PCI_MSI_FLAGS_64BIT))
+		dev->no_64bit_msi = 1;
 }
 
 void pci_msix_init(struct pci_dev *dev)
-- 
2.25.1