PCI/MSI: Return -ENOSPC from pci_alloc_irq_vectors_affinity()

Ming Lei · bjorn-helgaas · commit 77f88abd4a6f · 2019-01-15T17:31:29.000-06:00
The API of pci_alloc_irq_vectors_affinity() says it returns -ENOSPC if fewer than @min_vecs interrupt vectors are available for @dev. However, if a device supports MSI-X but not MSI and a caller requests @min_vecs that can't be satisfied by MSI-X, we previously returned -EINVAL (from the failed attempt to enable MSI), not -ENOSPC. When -ENOSPC is returned, callers may reduce the number IRQs they request and try again. Most callers can use the @min_vecs and @max_vecs parameters to avoid this retry loop, but that doesn't work when using IRQ affinity "nr_sets" because rebalancing the sets is driver-specific. This return value bug has been present since pci_alloc_irq_vectors() was added in v4.10 by aff1716 ("PCI: Provide sensible IRQ vector alloc/free routines"), but it wasn't an issue because @min_vecs/@max_vecs removed the need for callers to iteratively reduce the number of IRQs requested and retry the allocation, so they didn't need to distinguish -ENOSPC from -EINVAL. In v5.0, 6da4b3a ("genirq/affinity: Add support for allocating interrupt sets") added IRQ sets to the interface, which reintroduced the need to check for -ENOSPC and possibly reduce the number of IRQs requested and retry the allocation. Signed-off-by: Ming Lei <ming.lei@redhat.com> [bhelgaas: changelog] Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Cc: Jens Axboe <axboe@fb.com> Cc: Keith Busch <keith.busch@intel.com> Cc: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
@@ -1168,7 +1168,8 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 				   const struct irq_affinity *affd)
 {
 	static const struct irq_affinity msi_default_affd;
-	int vecs = -ENOSPC;
+	int msix_vecs = -ENOSPC;
+	int msi_vecs = -ENOSPC;
 
 	if (flags & PCI_IRQ_AFFINITY) {
 		if (!affd)
@@ -1179,16 +1180,17 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 	}
 
 	if (flags & PCI_IRQ_MSIX) {
-		vecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
-				affd);
-		if (vecs > 0)
-			return vecs;
+		msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
+						    max_vecs, affd);
+		if (msix_vecs > 0)
+			return msix_vecs;
 	}
 
 	if (flags & PCI_IRQ_MSI) {
-		vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);
-		if (vecs > 0)
-			return vecs;
+		msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,
+						  affd);
+		if (msi_vecs > 0)
+			return msi_vecs;
 	}
 
 	/* use legacy irq if allowed */
@@ -1199,7 +1201,9 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 		}
 	}
 
-	return vecs;
+	if (msix_vecs == -ENOSPC)
+		return -ENOSPC;
+	return msi_vecs;
 }
 EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);
 

Original file line number	Diff line number	Diff line change
`@@ -1168,7 +1168,8 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,`
`1168`	`1168`	`const struct irq_affinity *affd)`
`1169`	`1169`	`{`
`1170`	`1170`	`static const struct irq_affinity msi_default_affd;`
`1171`		`- int vecs = -ENOSPC;`
	`1171`	`+ int msix_vecs = -ENOSPC;`
	`1172`	`+ int msi_vecs = -ENOSPC;`
`1172`	`1173`
`1173`	`1174`	`if (flags & PCI_IRQ_AFFINITY) {`
`1174`	`1175`	`if (!affd)`
`@@ -1179,16 +1180,17 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,`
`1179`	`1180`	`}`
`1180`	`1181`
`1181`	`1182`	`if (flags & PCI_IRQ_MSIX) {`
`1182`		`- vecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,`
`1183`		`- affd);`
`1184`		`- if (vecs > 0)`
`1185`		`- return vecs;`
	`1183`	`+ msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,`
	`1184`	`+ max_vecs, affd);`
	`1185`	`+ if (msix_vecs > 0)`
	`1186`	`+ return msix_vecs;`
`1186`	`1187`	`}`
`1187`	`1188`
`1188`	`1189`	`if (flags & PCI_IRQ_MSI) {`
`1189`		`- vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);`
`1190`		`- if (vecs > 0)`
`1191`		`- return vecs;`
	`1190`	`+ msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,`
	`1191`	`+ affd);`
	`1192`	`+ if (msi_vecs > 0)`
	`1193`	`+ return msi_vecs;`
`1192`	`1194`	`}`
`1193`	`1195`
`1194`	`1196`	`/* use legacy irq if allowed */`
`@@ -1199,7 +1201,9 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,`
`1199`	`1201`	`}`
`1200`	`1202`	`}`
`1201`	`1203`
`1202`		`- return vecs;`
	`1204`	`+ if (msix_vecs == -ENOSPC)`
	`1205`	`+ return -ENOSPC;`
	`1206`	`+ return msi_vecs;`
`1203`	`1207`	`}`
`1204`	`1208`	`EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);`
`1205`	`1209`