[tip: irq/urgent] PCI/MSI: Deal with devices lying about their MSI mask capability

["tip-bot2 for Marc Zyngier" <tip-bot2@linutronix.de>]

The following commit has been merged into the irq/urgent branch of tip:

Commit-ID:     2226667a145db2e1f314d7f57fd644fe69863ab9
Gitweb:        https://git.kernel.org/tip/2226667a145db2e1f314d7f57fd644fe69863ab9
Author:        Marc Zyngier <maz@kernel.org>
AuthorDate:    Thu, 04 Nov 2021 18:01:29 
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 11 Nov 2021 09:50:30 +01:00

PCI/MSI: Deal with devices lying about their MSI mask capability

It appears that some devices are lying about their mask capability,
pretending that they don't have it, while they actually do.
The net result is that now that we don't enable MSIs on such
endpoint.

Add a new per-device flag to deal with this. Further patches will
make use of it, sadly.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20211104180130.3825416-2-maz@kernel.org
Cc: Bjorn Helgaas <helgaas@kernel.org>
---
 drivers/pci/msi.c   | 3 +++
 include/linux/pci.h | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 6da7910..7043301 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -477,6 +477,9 @@ msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)
 		goto out;
 
 	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
+	/* Lies, damned lies, and MSIs */
+	if (dev->dev_flags & PCI_DEV_FLAGS_HAS_MSI_MASKING)
+		control |= PCI_MSI_FLAGS_MASKBIT;
 
 	entry->msi_attrib.is_msix	= 0;
 	entry->msi_attrib.is_64		= !!(control & PCI_MSI_FLAGS_64BIT);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c8afbee..d0dba7f 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -233,6 +233,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_NO_FLR_RESET = (__force pci_dev_flags_t) (1 << 10),
 	/* Don't use Relaxed Ordering for TLPs directed at this device */
 	PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11),
+	/* Device does honor MSI masking despite saying otherwise */
+	PCI_DEV_FLAGS_HAS_MSI_MASKING = (__force pci_dev_flags_t) (1 << 12),
 };
 
 enum pci_irq_reroute_variant {