diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index a8d0100..10a9369 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -82,7 +82,19 @@
 has to request that the PCI layer set up the MSI capability for this
 device.
 
-4.2.1 pci_enable_msi_range
+4.2.1 pci_enable_msi
+
+int pci_enable_msi(struct pci_dev *dev)
+
+A successful call allocates ONE interrupt to the device, regardless
+of how many MSIs the device supports.  The device is switched from
+pin-based interrupt mode to MSI mode.  The dev->irq number is changed
+to a new number which represents the message signaled interrupt;
+consequently, this function should be called before the driver calls
+request_irq(), because an MSI is delivered via a vector that is
+different from the vector of a pin-based interrupt.
+
+4.2.2 pci_enable_msi_range
 
 int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
 
@@ -147,6 +159,11 @@
 	return pci_enable_msi_range(pdev, nvec, nvec);
 }
 
+Note, unlike pci_enable_msi_exact() function, which could be also used to
+enable a particular number of MSI-X interrupts, pci_enable_msi_range()
+returns either a negative errno or 'nvec' (not negative errno or 0 - as
+pci_enable_msi_exact() does).
+
 4.2.1.3 Single MSI mode
 
 The most notorious example of the request type described above is
@@ -158,7 +175,27 @@
 	return pci_enable_msi_range(pdev, 1, 1);
 }
 
-4.2.2 pci_disable_msi
+Note, unlike pci_enable_msi() function, which could be also used to
+enable the single MSI mode, pci_enable_msi_range() returns either a
+negative errno or 1 (not negative errno or 0 - as pci_enable_msi()
+does).
+
+4.2.3 pci_enable_msi_exact
+
+int pci_enable_msi_exact(struct pci_dev *dev, int nvec)
+
+This variation on pci_enable_msi_range() call allows a device driver to
+request exactly 'nvec' MSIs.
+
+If this function returns a negative number, it indicates an error and
+the driver should not attempt to request any more MSI interrupts for
+this device.
+
+By contrast with pci_enable_msi_range() function, pci_enable_msi_exact()
+returns zero in case of success, which indicates MSI interrupts have been
+successfully allocated.
+
+4.2.4 pci_disable_msi
 
 void pci_disable_msi(struct pci_dev *dev)
 
@@ -172,7 +209,7 @@
 Failure to do so results in a BUG_ON(), leaving the device with
 MSI enabled and thus leaking its vector.
 
-4.2.3 pci_msi_vec_count
+4.2.4 pci_msi_vec_count
 
 int pci_msi_vec_count(struct pci_dev *dev)
 
@@ -257,8 +294,8 @@
 
 static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
 {
-	return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
-				    1, nvec);
+	return pci_enable_msix_range(adapter->pdev, adapter->msix_entries,
+				     1, nvec);
 }
 
 Note the value of 'minvec' parameter is 1.  As 'minvec' is inclusive,
@@ -269,8 +306,8 @@
 
 static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
 {
-	return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
-				    FOO_DRIVER_MINIMUM_NVEC, nvec);
+	return pci_enable_msix_range(adapter->pdev, adapter->msix_entries,
+				     FOO_DRIVER_MINIMUM_NVEC, nvec);
 }
 
 4.3.1.2 Exact number of MSI-X interrupts
@@ -282,10 +319,15 @@
 
 static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
 {
-	return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
-				    nvec, nvec);
+	return pci_enable_msix_range(adapter->pdev, adapter->msix_entries,
+				     nvec, nvec);
 }
 
+Note, unlike pci_enable_msix_exact() function, which could be also used to
+enable a particular number of MSI-X interrupts, pci_enable_msix_range()
+returns either a negative errno or 'nvec' (not negative errno or 0 - as
+pci_enable_msix_exact() does).
+
 4.3.1.3 Specific requirements to the number of MSI-X interrupts
 
 As noted above, there could be devices that can not operate with just any
@@ -332,7 +374,64 @@
 any error code other than -ENOSPC indicates a fatal error and should not
 be retried.
 
-4.3.2 pci_disable_msix
+4.3.2 pci_enable_msix_exact
+
+int pci_enable_msix_exact(struct pci_dev *dev,
+			  struct msix_entry *entries, int nvec)
+
+This variation on pci_enable_msix_range() call allows a device driver to
+request exactly 'nvec' MSI-Xs.
+
+If this function returns a negative number, it indicates an error and
+the driver should not attempt to allocate any more MSI-X interrupts for
+this device.
+
+By contrast with pci_enable_msix_range() function, pci_enable_msix_exact()
+returns zero in case of success, which indicates MSI-X interrupts have been
+successfully allocated.
+
+Another version of a routine that enables MSI-X mode for a device with
+specific requirements described in chapter 4.3.1.3 might look like this:
+
+/*
+ * Assume 'minvec' and 'maxvec' are non-zero
+ */
+static int foo_driver_enable_msix(struct foo_adapter *adapter,
+				  int minvec, int maxvec)
+{
+	int rc;
+
+	minvec = roundup_pow_of_two(minvec);
+	maxvec = rounddown_pow_of_two(maxvec);
+
+	if (minvec > maxvec)
+		return -ERANGE;
+
+retry:
+	rc = pci_enable_msix_exact(adapter->pdev,
+				   adapter->msix_entries, maxvec);
+
+	/*
+	 * -ENOSPC is the only error code allowed to be analyzed
+	 */
+	if (rc == -ENOSPC) {
+		if (maxvec == 1)
+			return -ENOSPC;
+
+		maxvec /= 2;
+
+		if (minvec > maxvec)
+			return -ENOSPC;
+
+		goto retry;
+	} else if (rc < 0) {
+		return rc;
+	}
+
+	return maxvec;
+}
+
+4.3.3 pci_disable_msix
 
 void pci_disable_msix(struct pci_dev *dev)
 
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index dc2756f..0237109 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1151,13 +1151,13 @@
 static int ahci_init_interrupts(struct pci_dev *pdev, unsigned int n_ports,
 			 struct ahci_host_priv *hpriv)
 {
-	int rc, nvec;
+	int nvec;
 
 	if (hpriv->flags & AHCI_HFLAG_NO_MSI)
 		goto intx;
 
-	rc = pci_msi_vec_count(pdev);
-	if (rc < 0)
+	nvec = pci_msi_vec_count(pdev);
+	if (nvec < 0)
 		goto intx;
 
 	/*
@@ -1165,19 +1165,19 @@
 	 * Message mode could be enforced. In this case assume that advantage
 	 * of multipe MSIs is negated and use single MSI mode instead.
 	 */
-	if (rc < n_ports)
+	if (nvec < n_ports)
 		goto single_msi;
 
-	nvec = rc;
-	rc = pci_enable_msi_block(pdev, nvec);
-	if (rc)
+	nvec = pci_enable_msi_range(pdev, nvec, nvec);
+	if (nvec == -ENOSPC)
+		goto single_msi;
+	else if (nvec < 0)
 		goto intx;
 
 	return nvec;
 
 single_msi:
-	rc = pci_enable_msi(pdev);
-	if (rc)
+	if (pci_enable_msi(pdev))
 		goto intx;
 	return 1;
 
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 7a0fec6..955ab79 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -545,9 +545,15 @@
 		return -ENOMEM;
 	list_for_each_entry(entry, &pdev->msi_list, list) {
 		char *name = kmalloc(20, GFP_KERNEL);
-		msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
-		if (!msi_dev_attr)
+		if (!name)
 			goto error_attrs;
+
+		msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
+		if (!msi_dev_attr) {
+			kfree(name);
+			goto error_attrs;
+		}
+
 		sprintf(name, "%d", entry->irq);
 		sysfs_attr_init(&msi_dev_attr->attr);
 		msi_dev_attr->attr.name = name;
@@ -589,6 +595,7 @@
 		++count;
 		msi_attr = msi_attrs[count];
 	}
+	kfree(msi_attrs);
 	return ret;
 }
 
@@ -959,7 +966,6 @@
 /**
  * pci_msix_vec_count - return the number of device's MSI-X table entries
  * @dev: pointer to the pci_dev data structure of MSI-X device function
-
  * This function returns the number of device's MSI-X table entries and
  * therefore the number of MSI-X vectors device is capable of sending.
  * It returns a negative errno if the device is not capable of sending MSI-X
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 2103576..9dd49c9 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -482,15 +482,19 @@
 		for (i = 0; i < nvec; i++)
 			vdev->msix[i].entry = i;
 
-		ret = pci_enable_msix(pdev, vdev->msix, nvec);
-		if (ret) {
+		ret = pci_enable_msix_range(pdev, vdev->msix, 1, nvec);
+		if (ret < nvec) {
+			if (ret > 0)
+				pci_disable_msix(pdev);
 			kfree(vdev->msix);
 			kfree(vdev->ctx);
 			return ret;
 		}
 	} else {
-		ret = pci_enable_msi_block(pdev, nvec);
-		if (ret) {
+		ret = pci_enable_msi_range(pdev, 1, nvec);
+		if (ret < nvec) {
+			if (ret > 0)
+				pci_disable_msi(pdev);
 			kfree(vdev->ctx);
 			return ret;
 		}
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 60ab8d7..1e26fc6 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1171,8 +1171,23 @@
 void pci_restore_msi_state(struct pci_dev *dev);
 int pci_msi_enabled(void);
 int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec);
+static inline int pci_enable_msi_exact(struct pci_dev *dev, int nvec)
+{
+	int rc = pci_enable_msi_range(dev, nvec, nvec);
+	if (rc < 0)
+		return rc;
+	return 0;
+}
 int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
 			  int minvec, int maxvec);
+static inline int pci_enable_msix_exact(struct pci_dev *dev,
+					struct msix_entry *entries, int nvec)
+{
+	int rc = pci_enable_msix_range(dev, entries, nvec, nvec);
+	if (rc < 0)
+		return rc;
+	return 0;
+}
 #else
 static inline int pci_msi_vec_count(struct pci_dev *dev) { return -ENOSYS; }
 static inline int pci_enable_msi_block(struct pci_dev *dev, int nvec)
@@ -1191,9 +1206,14 @@
 static inline int pci_enable_msi_range(struct pci_dev *dev, int minvec,
 				       int maxvec)
 { return -ENOSYS; }
+static inline int pci_enable_msi_exact(struct pci_dev *dev, int nvec)
+{ return -ENOSYS; }
 static inline int pci_enable_msix_range(struct pci_dev *dev,
 		      struct msix_entry *entries, int minvec, int maxvec)
 { return -ENOSYS; }
+static inline int pci_enable_msix_exact(struct pci_dev *dev,
+		      struct msix_entry *entries, int nvec)
+{ return -ENOSYS; }
 #endif
 
 #ifdef CONFIG_PCIEPORTBUS