PCI/MSI: Validate MSI-X contiguous restriction early

With interrupt domains the sanity check for MSI-X vector validation can be
done _before_ any allocation happens. The sanity check only applies to the
allocation functions which have an 'entries' array argument. The entries
array is filled by the caller with the requested MSI-X indices. Some drivers
have gaps in the index space which is not supported on all architectures.

The PCI/MSI irq domain has a 'feature' bit to enforce this validation late
during the allocation phase.

Just do it right away before doing any other work along with the other
sanity checks on that array.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20221111122015.691357406@linutronix.de

drivers/pci/msi/msi.c

@@ -725,13 +725,17 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
 	return ret;
 }
 
-static bool pci_msix_validate_entries(struct msix_entry *entries, int nvec, int hwsize)
+static bool pci_msix_validate_entries(struct pci_dev *dev, struct msix_entry *entries,
+				      int nvec, int hwsize)
 {
+	bool nogap;
 	int i, j;
 
 	if (!entries)
 		return true;
 
+	nogap = pci_msi_domain_supports(dev, MSI_FLAG_MSIX_CONTIGUOUS, DENY_LEGACY);
+
 	for (i = 0; i < nvec; i++) {
 		/* Entry within hardware limit? */
 		if (entries[i].entry >= hwsize)
@@ -742,6 +746,9 @@ static bool pci_msix_validate_entries(struct msix_entry *entries, int nvec, int
 			if (entries[i].entry == entries[j].entry)
 				return false;
 		}
+		/* Check for unsupported gaps */
+		if (nogap && entries[i].entry != i)
+			return false;
 	}
 	return true;
 }
@@ -773,7 +780,7 @@ int __pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries, int
 	if (hwsize < 0)
 		return hwsize;
 
-	if (!pci_msix_validate_entries(entries, nvec, hwsize))
+	if (!pci_msix_validate_entries(dev, entries, nvec, hwsize))
 		return -EINVAL;
 
 	/* PCI_IRQ_VIRTUAL is a horrible hack! */