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>

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 6da791022d2e3f7ccfe1765f96a1d1d4d251be6a..70433013897bbb1b69f74658bdecc21ee6c80c33 100644 (file)
--- 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 c8afbee5da4bfc0912336585326afb071bf02869..d0dba7fd98481ffb30598599f45ca48ab9c16f22 100644 (file)
--- 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 {