PCI/MSI: Provide MSI_FLAG_MSIX_CONTIGUOUS

Provide a domain info flag which makes the core code check for a contiguous
MSI-X index on allocation. That's simpler than checking it at some other
domain callback in architecture code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20211210221814.662401116@linutronix.de

drivers/pci/msi/irqdomain.c

@@ -89,9 +89,21 @@ static int pci_msi_domain_check_cap(struct irq_domain *domain,
 	if (pci_msi_desc_is_multi_msi(desc) &&
 	    !(info->flags & MSI_FLAG_MULTI_PCI_MSI))
 		return 1;
-	else if (desc->pci.msi_attrib.is_msix && !(info->flags & MSI_FLAG_PCI_MSIX))
-		return -ENOTSUPP;
 
+	if (desc->pci.msi_attrib.is_msix) {
+		if (!(info->flags & MSI_FLAG_PCI_MSIX))
+			return -ENOTSUPP;
+
+		if (info->flags & MSI_FLAG_MSIX_CONTIGUOUS) {
+			unsigned int idx = 0;
+
+			/* Check for gaps in the entry indices */
+			for_each_msi_entry(desc, dev) {
+				if (desc->msi_index != idx++)
+					return -ENOTSUPP;
+			}
+		}
+	}
 	return 0;
 }
 

include/linux/msi.h

@@ -362,6 +362,8 @@ enum {
 	MSI_FLAG_LEVEL_CAPABLE		= (1 << 6),
 	/* Populate sysfs on alloc() and destroy it on free() */
 	MSI_FLAG_DEV_SYSFS		= (1 << 7),
+	/* MSI-X entries must be contiguous */
+	MSI_FLAG_MSIX_CONTIGUOUS	= (1 << 8),
 };
 
 int msi_domain_set_affinity(struct irq_data *data, const struct cpumask *mask,