Virtualization - Nov 2016 - virtio_pci irq handling cleanups

Hi Michael,

this series contains a couple cleanups for the virtio_pci interrupt
handling code, including a switch to the new pci_irq_alloc_vectors
helper.  All these are in preparation of taking advantage of the new
PCI layer / core IRQ interrupt affinity handling, for which I will
send out a series once this and some core interrupt handling changes
are in.

This avoids the separate allocation for the msix_entries structures, and
instead allows us to use pci_irq_vector to find a given IRQ vector.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 42 +++++++++++++++-----------------------
 drivers/virtio/virtio_pci_common.h |  1 -
 2 files changed, 17 insertions(+), 26 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index d9a9058..f5e2751 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -37,7 +37,7 @@ void vp_synchronize_vectors(struct virtio_device *vdev)
 		synchronize_irq(vp_dev->pci_dev->irq);
 
 	for (i = 0; i < vp_dev->msix_vectors; ++i)
-		synchronize_irq(vp_dev->msix_entries[i].vector);
+		synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i));
 }
 
 /* the notify function used when creating a virt queue */
@@ -113,7 +113,7 @@ static void vp_free_vectors(struct virtio_device *vdev)
 	}
 
 	for (i = 0; i < vp_dev->msix_used_vectors; ++i)
-		free_irq(vp_dev->msix_entries[i].vector, vp_dev);
+		free_irq(pci_irq_vector(vp_dev->pci_dev, i), vp_dev);
 
 	for (i = 0; i < vp_dev->msix_vectors; i++)
 		if (vp_dev->msix_affinity_masks[i])
@@ -123,7 +123,7 @@ static void vp_free_vectors(struct virtio_device *vdev)
 		/* Disable the vector used for configuration */
 		vp_dev->config_vector(vp_dev, VIRTIO_MSI_NO_VECTOR);
 
-		pci_disable_msix(vp_dev->pci_dev);
+		pci_free_irq_vectors(vp_dev->pci_dev);
 		vp_dev->msix_enabled = 0;
 	}
 
@@ -131,8 +131,6 @@ static void vp_free_vectors(struct virtio_device *vdev)
 	vp_dev->msix_used_vectors = 0;
 	kfree(vp_dev->msix_names);
 	vp_dev->msix_names = NULL;
-	kfree(vp_dev->msix_entries);
-	vp_dev->msix_entries = NULL;
 	kfree(vp_dev->msix_affinity_masks);
 	vp_dev->msix_affinity_masks = NULL;
 }
@@ -147,10 +145,6 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 
 	vp_dev->msix_vectors = nvectors;
 
-	vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries,
-				       GFP_KERNEL);
-	if (!vp_dev->msix_entries)
-		goto error;
 	vp_dev->msix_names = kmalloc(nvectors * sizeof *vp_dev->msix_names,
 				     GFP_KERNEL);
 	if (!vp_dev->msix_names)
@@ -165,12 +159,9 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 					GFP_KERNEL))
 			goto error;
 
-	for (i = 0; i < nvectors; ++i)
-		vp_dev->msix_entries[i].entry = i;
-
-	err = pci_enable_msix_exact(vp_dev->pci_dev,
-				    vp_dev->msix_entries, nvectors);
-	if (err)
+	err = pci_alloc_irq_vectors(vp_dev->pci_dev, nvectors, nvectors,
+			PCI_IRQ_MSIX);
+	if (err < 0)
 		goto error;
 	vp_dev->msix_enabled = 1;
 
@@ -178,7 +169,7 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 	v = vp_dev->msix_used_vectors;
 	snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
 		 "%s-config", name);
-	err = request_irq(vp_dev->msix_entries[v].vector,
+	err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
 			  vp_config_changed, 0, vp_dev->msix_names[v],
 			  vp_dev);
 	if (err)
@@ -197,7 +188,7 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 		v = vp_dev->msix_used_vectors;
 		snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
 			 "%s-virtqueues", name);
-		err = request_irq(vp_dev->msix_entries[v].vector,
+		err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
 				  vp_vring_interrupt, 0, vp_dev->msix_names[v],
 				  vp_dev);
 		if (err)
@@ -276,14 +267,15 @@ void vp_del_vqs(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	struct virtqueue *vq, *n;
-	struct virtio_pci_vq_info *info;
 
 	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
-		info = vp_dev->vqs[vq->index];
-		if (vp_dev->per_vq_vectors &&
-			info->msix_vector != VIRTIO_MSI_NO_VECTOR)
-			free_irq(vp_dev->msix_entries[info->msix_vector].vector,
-				 vq);
+		if (vp_dev->per_vq_vectors) {
+			int v = vp_dev->vqs[vq->index]->msix_vector;
+
+			if (v != VIRTIO_MSI_NO_VECTOR)
+				free_irq(pci_irq_vector(vp_dev->pci_dev, v),
+					vq);
+		}
 		vp_del_vq(vq);
 	}
 	vp_dev->per_vq_vectors = false;
@@ -356,7 +348,7 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev,
unsigned nvqs,
 			 sizeof *vp_dev->msix_names,
 			 "%s-%s",
 			 dev_name(&vp_dev->vdev.dev), names[i]);
-		err = request_irq(vp_dev->msix_entries[msix_vec].vector,
+		err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec),
 				  vring_interrupt, 0,
 				  vp_dev->msix_names[msix_vec],
 				  vqs[i]);
@@ -419,7 +411,7 @@ int vp_set_vq_affinity(struct virtqueue *vq, int cpu)
 
 	if (vp_dev->msix_enabled) {
 		mask = vp_dev->msix_affinity_masks[info->msix_vector];
-		irq = vp_dev->msix_entries[info->msix_vector].vector;
+		irq = pci_irq_vector(vp_dev->pci_dev, info->msix_vector);
 		if (cpu == -1)
 			irq_set_affinity_hint(irq, NULL);
 		else {
diff --git a/drivers/virtio/virtio_pci_common.h
b/drivers/virtio/virtio_pci_common.h
index 2826320..b2f6662 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -85,7 +85,6 @@ struct virtio_pci_device {
 	/* MSI-X support */
 	int msix_enabled;
 	int intx_enabled;
-	struct msix_entry *msix_entries;
 	cpumask_var_t *msix_affinity_masks;
 	/* Name strings for interrupts. This size should be enough,
 	 * and I'm too lazy to allocate each name separately. */
-- 
2.1.4

vp_request_msix_vectors is only called by vp_try_to_find_vqs, which already
calls vp_free_vectors through vp_del_vqs in the failure case.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index f5e2751..93700c5 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -197,7 +197,6 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 	}
 	return 0;
 error:
-	vp_free_vectors(vdev);
 	return err;
 }
 
-- 
2.1.4

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 61 +++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 34 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index 93700c5..f6c5499 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -102,39 +102,6 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
 	return vp_vring_interrupt(irq, opaque);
 }
 
-static void vp_free_vectors(struct virtio_device *vdev)
-{
-	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-	int i;
-
-	if (vp_dev->intx_enabled) {
-		free_irq(vp_dev->pci_dev->irq, vp_dev);
-		vp_dev->intx_enabled = 0;
-	}
-
-	for (i = 0; i < vp_dev->msix_used_vectors; ++i)
-		free_irq(pci_irq_vector(vp_dev->pci_dev, i), vp_dev);
-
-	for (i = 0; i < vp_dev->msix_vectors; i++)
-		if (vp_dev->msix_affinity_masks[i])
-			free_cpumask_var(vp_dev->msix_affinity_masks[i]);
-
-	if (vp_dev->msix_enabled) {
-		/* Disable the vector used for configuration */
-		vp_dev->config_vector(vp_dev, VIRTIO_MSI_NO_VECTOR);
-
-		pci_free_irq_vectors(vp_dev->pci_dev);
-		vp_dev->msix_enabled = 0;
-	}
-
-	vp_dev->msix_vectors = 0;
-	vp_dev->msix_used_vectors = 0;
-	kfree(vp_dev->msix_names);
-	vp_dev->msix_names = NULL;
-	kfree(vp_dev->msix_affinity_masks);
-	vp_dev->msix_affinity_masks = NULL;
-}
-
 static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
 				   bool per_vq_vectors)
 {
@@ -266,6 +233,7 @@ void vp_del_vqs(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	struct virtqueue *vq, *n;
+	int i;
 
 	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
 		if (vp_dev->per_vq_vectors) {
@@ -279,7 +247,32 @@ void vp_del_vqs(struct virtio_device *vdev)
 	}
 	vp_dev->per_vq_vectors = false;
 
-	vp_free_vectors(vdev);
+	if (vp_dev->intx_enabled) {
+		free_irq(vp_dev->pci_dev->irq, vp_dev);
+		vp_dev->intx_enabled = 0;
+	}
+
+	for (i = 0; i < vp_dev->msix_used_vectors; ++i)
+		free_irq(pci_irq_vector(vp_dev->pci_dev, i), vp_dev);
+
+	for (i = 0; i < vp_dev->msix_vectors; i++)
+		if (vp_dev->msix_affinity_masks[i])
+			free_cpumask_var(vp_dev->msix_affinity_masks[i]);
+
+	if (vp_dev->msix_enabled) {
+		/* Disable the vector used for configuration */
+		vp_dev->config_vector(vp_dev, VIRTIO_MSI_NO_VECTOR);
+
+		pci_free_irq_vectors(vp_dev->pci_dev);
+		vp_dev->msix_enabled = 0;
+	}
+
+	vp_dev->msix_vectors = 0;
+	vp_dev->msix_used_vectors = 0;
+	kfree(vp_dev->msix_names);
+	vp_dev->msix_names = NULL;
+	kfree(vp_dev->msix_affinity_masks);
+	vp_dev->msix_affinity_masks = NULL;
 	kfree(vp_dev->vqs);
 	vp_dev->vqs = NULL;
 }
-- 
2.1.4

There is basically no shared logic with the two MSI-X variants, so move
it into a separate function.  Also remove the fairly pointless
vp_request_intx wrapper while we're at it.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 89 ++++++++++++++++++++++----------------
 1 file changed, 52 insertions(+), 37 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index f6c5499..644bd80 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -167,18 +167,6 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 	return err;
 }
 
-static int vp_request_intx(struct virtio_device *vdev)
-{
-	int err;
-	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-
-	err = request_irq(vp_dev->pci_dev->irq, vp_interrupt,
-			  IRQF_SHARED, dev_name(&vdev->dev), vp_dev);
-	if (!err)
-		vp_dev->intx_enabled = 1;
-	return err;
-}
-
 static struct virtqueue *vp_setup_vq(struct virtio_device *vdev, unsigned
index,
 				     void (*callback)(struct virtqueue *vq),
 				     const char *name,
@@ -281,7 +269,6 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev,
unsigned nvqs,
 			      struct virtqueue *vqs[],
 			      vq_callback_t *callbacks[],
 			      const char * const names[],
-			      bool use_msix,
 			      bool per_vq_vectors)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
@@ -292,28 +279,21 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev,
unsigned nvqs,
 	if (!vp_dev->vqs)
 		return -ENOMEM;
 
-	if (!use_msix) {
-		/* Old style: one normal interrupt for change and all vqs. */
-		err = vp_request_intx(vdev);
-		if (err)
-			goto error_find;
+	if (per_vq_vectors) {
+		/* Best option: one for change interrupt, one per vq. */
+		nvectors = 1;
+		for (i = 0; i < nvqs; ++i)
+			if (callbacks[i])
+				++nvectors;
 	} else {
-		if (per_vq_vectors) {
-			/* Best option: one for change interrupt, one per vq. */
-			nvectors = 1;
-			for (i = 0; i < nvqs; ++i)
-				if (callbacks[i])
-					++nvectors;
-		} else {
-			/* Second best: one for change, shared for all vqs. */
-			nvectors = 2;
-		}
-
-		err = vp_request_msix_vectors(vdev, nvectors, per_vq_vectors);
-		if (err)
-			goto error_find;
+		/* Second best: one for change, shared for all vqs. */
+		nvectors = 2;
 	}
 
+	err = vp_request_msix_vectors(vdev, nvectors, per_vq_vectors);
+	if (err)
+		goto error_find;
+
 	vp_dev->per_vq_vectors = per_vq_vectors;
 	allocated_vectors = vp_dev->msix_used_vectors;
 	for (i = 0; i < nvqs; ++i) {
@@ -356,6 +336,43 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev,
unsigned nvqs,
 	return err;
 }
 
+static int vp_find_vqs_intx(struct virtio_device *vdev, unsigned nvqs,
+		struct virtqueue *vqs[], vq_callback_t *callbacks[],
+		const char * const names[])
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	int i, err;
+
+	vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
+	if (!vp_dev->vqs)
+		return -ENOMEM;
+
+	err = request_irq(vp_dev->pci_dev->irq, vp_interrupt, IRQF_SHARED,
+			dev_name(&vdev->dev), vp_dev);
+	if (err)
+		goto out_del_vqs;
+
+	vp_dev->intx_enabled = 1;
+	vp_dev->per_vq_vectors = false;
+	for (i = 0; i < nvqs; ++i) {
+		if (!names[i]) {
+			vqs[i] = NULL;
+			continue;
+		}
+		vqs[i] = vp_setup_vq(vdev, i, callbacks[i], names[i],
+				VIRTIO_MSI_NO_VECTOR);
+		if (IS_ERR(vqs[i])) {
+			err = PTR_ERR(vqs[i]);
+			goto out_del_vqs;
+		}
+	}
+
+	return 0;
+out_del_vqs:
+	vp_del_vqs(vdev);
+	return err;
+}
+
 /* the config->find_vqs() implementation */
 int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 		struct virtqueue *vqs[],
@@ -365,17 +382,15 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 	int err;
 
 	/* Try MSI-X with one vector per queue. */
-	err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, true, true);
+	err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, true);
 	if (!err)
 		return 0;
 	/* Fallback: MSI-X with one vector for config, one shared for queues. */
-	err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
-				 true, false);
+	err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, false);
 	if (!err)
 		return 0;
 	/* Finally fall back to regular interrupts. */
-	return vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
-				  false, false);
+	return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names);
 }
 
 const char *vp_bus_name(struct virtio_device *vdev)
-- 
2.1.4

Factor out some duplicated code to format that MSI-X vector name and
request the interrupt for it.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 38 +++++++++++++++-----------------------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index 644bd80..7c44891 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -102,11 +102,19 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
 	return vp_vring_interrupt(irq, opaque);
 }
 
+static int vp_request_msix_vector(struct virtio_pci_device *vp_dev, int vec,
+		irq_handler_t handler, const char *name, void *dev_id)
+{
+	snprintf(vp_dev->msix_names[vec], sizeof(vp_dev->msix_names[vec]),
+			"%s-%s", dev_name(&vp_dev->vdev.dev), name);
+	return request_irq(pci_irq_vector(vp_dev->pci_dev, vec), handler, 0,
+			vp_dev->msix_names[vec], dev_id);
+}
+
 static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
 				   bool per_vq_vectors)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-	const char *name = dev_name(&vp_dev->vdev.dev);
 	unsigned i, v;
 	int err = -ENOMEM;
 
@@ -133,15 +141,10 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 	vp_dev->msix_enabled = 1;
 
 	/* Set the vector used for configuration */
-	v = vp_dev->msix_used_vectors;
-	snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
-		 "%s-config", name);
-	err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
-			  vp_config_changed, 0, vp_dev->msix_names[v],
-			  vp_dev);
+	err = vp_request_msix_vector(vp_dev, vp_dev->msix_used_vectors++,
+			vp_config_changed, "config", vp_dev);
 	if (err)
 		goto error;
-	++vp_dev->msix_used_vectors;
 
 	v = vp_dev->config_vector(vp_dev, v);
 	/* Verify we had enough resources to assign the vector */
@@ -152,15 +155,10 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 
 	if (!per_vq_vectors) {
 		/* Shared vector for all VQs */
-		v = vp_dev->msix_used_vectors;
-		snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
-			 "%s-virtqueues", name);
-		err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
-				  vp_vring_interrupt, 0, vp_dev->msix_names[v],
-				  vp_dev);
+		err = vp_request_msix_vector(vp_dev, vp_dev->msix_used_vectors++,
+				vp_vring_interrupt, "virtqueues", vp_dev);
 		if (err)
 			goto error;
-		++vp_dev->msix_used_vectors;
 	}
 	return 0;
 error:
@@ -316,14 +314,8 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev,
unsigned nvqs,
 			continue;
 
 		/* allocate per-vq irq if available and necessary */
-		snprintf(vp_dev->msix_names[msix_vec],
-			 sizeof *vp_dev->msix_names,
-			 "%s-%s",
-			 dev_name(&vp_dev->vdev.dev), names[i]);
-		err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec),
-				  vring_interrupt, 0,
-				  vp_dev->msix_names[msix_vec],
-				  vqs[i]);
+		err = vp_request_msix_vector(vp_dev, msix_vec, vring_interrupt,
+				names[i], vqs[i]);
 		if (err) {
 			vp_del_vq(vqs[i]);
 			goto error_find;
-- 
2.1.4

While this is a tiny bit more code in terms of LOC it clearly separates
the purposes of both routines and makes them a lot easier to read, and
more importantly to modify for PCI-level affinity assignment which will
only go into the per-VQ version.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 103 +++++++++++++++++++++----------------
 1 file changed, 59 insertions(+), 44 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index 7c44891..3f166bc 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -111,8 +111,7 @@ static int vp_request_msix_vector(struct virtio_pci_device
*vp_dev, int vec,
 			vp_dev->msix_names[vec], dev_id);
 }
 
-static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
-				   bool per_vq_vectors)
+static int vp_setup_msix_vectors(struct virtio_device *vdev, int nvectors)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	unsigned i, v;
@@ -153,13 +152,6 @@ static int vp_request_msix_vectors(struct virtio_device
*vdev, int nvectors,
 		goto error;
 	}
 
-	if (!per_vq_vectors) {
-		/* Shared vector for all VQs */
-		err = vp_request_msix_vector(vp_dev, vp_dev->msix_used_vectors++,
-				vp_vring_interrupt, "virtqueues", vp_dev);
-		if (err)
-			goto error;
-	}
 	return 0;
 error:
 	return err;
@@ -263,67 +255,90 @@ void vp_del_vqs(struct virtio_device *vdev)
 	vp_dev->vqs = NULL;
 }
 
-static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
-			      struct virtqueue *vqs[],
-			      vq_callback_t *callbacks[],
-			      const char * const names[],
-			      bool per_vq_vectors)
+static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
+		struct virtqueue *vqs[], vq_callback_t *callbacks[],
+		const char * const names[])
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	int i, err, nvectors = 1, allocated_vectors;
 	u16 msix_vec;
-	int i, err, nvectors, allocated_vectors;
 
-	vp_dev->vqs = kmalloc(nvqs * sizeof *vp_dev->vqs, GFP_KERNEL);
+	vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
 	if (!vp_dev->vqs)
 		return -ENOMEM;
 
-	if (per_vq_vectors) {
-		/* Best option: one for change interrupt, one per vq. */
-		nvectors = 1;
-		for (i = 0; i < nvqs; ++i)
-			if (callbacks[i])
-				++nvectors;
-	} else {
-		/* Second best: one for change, shared for all vqs. */
-		nvectors = 2;
+	for (i = 0; i < nvqs; ++i) {
+		if (callbacks[i])
+			nvectors++;
 	}
-
-	err = vp_request_msix_vectors(vdev, nvectors, per_vq_vectors);
+	err = vp_setup_msix_vectors(vdev, nvectors);
 	if (err)
-		goto error_find;
+		goto out_del_vqs;
 
-	vp_dev->per_vq_vectors = per_vq_vectors;
+	vp_dev->per_vq_vectors = true;
 	allocated_vectors = vp_dev->msix_used_vectors;
 	for (i = 0; i < nvqs; ++i) {
-		if (!names[i]) {
-			vqs[i] = NULL;
+		if (!names[i])
 			continue;
-		} else if (!callbacks[i] || !vp_dev->msix_enabled)
+		if (!callbacks[i])
 			msix_vec = VIRTIO_MSI_NO_VECTOR;
-		else if (vp_dev->per_vq_vectors)
-			msix_vec = allocated_vectors++;
 		else
-			msix_vec = VP_MSIX_VQ_VECTOR;
+			msix_vec = allocated_vectors++;
+
 		vqs[i] = vp_setup_vq(vdev, i, callbacks[i], names[i], msix_vec);
 		if (IS_ERR(vqs[i])) {
 			err = PTR_ERR(vqs[i]);
-			goto error_find;
+			goto out_del_vqs;
 		}
-
-		if (!vp_dev->per_vq_vectors || msix_vec == VIRTIO_MSI_NO_VECTOR)
+		if (msix_vec == VIRTIO_MSI_NO_VECTOR)
 			continue;
-
-		/* allocate per-vq irq if available and necessary */
 		err = vp_request_msix_vector(vp_dev, msix_vec, vring_interrupt,
 				names[i], vqs[i]);
 		if (err) {
 			vp_del_vq(vqs[i]);
-			goto error_find;
+			goto out_del_vqs;
 		}
 	}
+
 	return 0;
+out_del_vqs:
+	vp_del_vqs(vdev);
+	return err;
+}
+
+static int vp_find_vqs_msix_shared(struct virtio_device *vdev, unsigned nvqs,
+		struct virtqueue *vqs[], vq_callback_t *callbacks[],
+		const char * const names[])
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	int i, err;
+
+	vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
+	if (!vp_dev->vqs)
+		return -ENOMEM;
+	err = vp_setup_msix_vectors(vdev, 2);
+	if (err)
+		goto out_del_vqs;
+	err = vp_request_msix_vector(vp_dev, vp_dev->msix_used_vectors++,
+			vp_vring_interrupt, "virtqueues", vp_dev);
+	if (err)
+		goto out_del_vqs;
 
-error_find:
+	vp_dev->per_vq_vectors = false;
+	for (i = 0; i < nvqs; ++i) {
+		if (!names[i])
+			continue;
+		vqs[i] = vp_setup_vq(vdev, i, callbacks[i], names[i],
+				callbacks[i] ? VP_MSIX_VQ_VECTOR :
+					VIRTIO_MSI_NO_VECTOR);
+		if (IS_ERR(vqs[i])) {
+			err = PTR_ERR(vqs[i]);
+			goto out_del_vqs;
+		}
+	}
+
+	return 0;
+out_del_vqs:
 	vp_del_vqs(vdev);
 	return err;
 }
@@ -374,11 +389,11 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 	int err;
 
 	/* Try MSI-X with one vector per queue. */
-	err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, true);
+	err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names);
 	if (!err)
 		return 0;
 	/* Fallback: MSI-X with one vector for config, one shared for queues. */
-	err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, false);
+	err = vp_find_vqs_msix_shared(vdev, nvqs, vqs, callbacks, names);
 	if (!err)
 		return 0;
 	/* Finally fall back to regular interrupts. */
-- 
2.1.4

Currently there is a lot of interrupt-related state in struct
virtio_pci_device, must of which is not needed:

 - msix_enabled is stored in struct pci_device and can be used there
 - msix_enabled isn't needed as we can call pci_free_irq_vectors even
   for the INTx case and it will do the right thing, as will a call
   to pci_irq_vector for vector 0
 - used_msix_vectors is not needed because we can just subtract the number
   of per-VQ vectors from the total number and get it
 - per_vq_vectors is not needed as we can just check the msix_vec field
   in the VQ for a valid vector

This just laves us with the old msix_vectors field that has been renamed
to irq_vectors and will be maintained for the INTx case as well to make
our life easier.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/virtio/virtio_pci_common.c | 64 ++++++++++++++------------------------
 drivers/virtio/virtio_pci_common.h | 12 ++-----
 drivers/virtio/virtio_pci_legacy.c |  2 +-
 drivers/virtio/virtio_pci_modern.c |  2 +-
 include/uapi/linux/virtio_pci.h    |  2 +-
 5 files changed, 29 insertions(+), 53 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index 3f166bc..4b2af83 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -33,10 +33,7 @@ void vp_synchronize_vectors(struct virtio_device *vdev)
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	int i;
 
-	if (vp_dev->intx_enabled)
-		synchronize_irq(vp_dev->pci_dev->irq);
-
-	for (i = 0; i < vp_dev->msix_vectors; ++i)
+	for (i = 0; i < vp_dev->irq_vectors; ++i)
 		synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i));
 }
 
@@ -117,8 +114,6 @@ static int vp_setup_msix_vectors(struct virtio_device *vdev,
int nvectors)
 	unsigned i, v;
 	int err = -ENOMEM;
 
-	vp_dev->msix_vectors = nvectors;
-
 	vp_dev->msix_names = kmalloc(nvectors * sizeof *vp_dev->msix_names,
 				     GFP_KERNEL);
 	if (!vp_dev->msix_names)
@@ -137,10 +132,9 @@ static int vp_setup_msix_vectors(struct virtio_device
*vdev, int nvectors)
 			PCI_IRQ_MSIX);
 	if (err < 0)
 		goto error;
-	vp_dev->msix_enabled = 1;
 
 	/* Set the vector used for configuration */
-	err = vp_request_msix_vector(vp_dev, vp_dev->msix_used_vectors++,
+	err = vp_request_msix_vector(vp_dev, vp_dev->irq_vectors++,
 			vp_config_changed, "config", vp_dev);
 	if (err)
 		goto error;
@@ -211,46 +205,40 @@ void vp_del_vqs(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	struct virtqueue *vq, *n;
+	int irq_vectors = vp_dev->irq_vectors;
 	int i;
 
 	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
-		if (vp_dev->per_vq_vectors) {
-			int v = vp_dev->vqs[vq->index]->msix_vector;
+		int vec = vp_dev->vqs[vq->index]->msix_vector;
 
-			if (v != VIRTIO_MSI_NO_VECTOR)
-				free_irq(pci_irq_vector(vp_dev->pci_dev, v),
-					vq);
+		if (vec != VIRTIO_MSI_NO_VECTOR && vec != VP_MSIX_VQ_VECTOR) {
+			free_irq(pci_irq_vector(vp_dev->pci_dev, vec), vq);
+			irq_vectors--;
 		}
-		vp_del_vq(vq);
-	}
-	vp_dev->per_vq_vectors = false;
 
-	if (vp_dev->intx_enabled) {
-		free_irq(vp_dev->pci_dev->irq, vp_dev);
-		vp_dev->intx_enabled = 0;
+		vp_del_vq(vq);
 	}
 
-	for (i = 0; i < vp_dev->msix_used_vectors; ++i)
+	for (i = irq_vectors - 1; i >= 0; i--)
 		free_irq(pci_irq_vector(vp_dev->pci_dev, i), vp_dev);
 
-	for (i = 0; i < vp_dev->msix_vectors; i++)
-		if (vp_dev->msix_affinity_masks[i])
+	if (vp_dev->msix_affinity_masks) {
+		for (i = 0; i < vp_dev->irq_vectors; i++)
 			free_cpumask_var(vp_dev->msix_affinity_masks[i]);
+		kfree(vp_dev->msix_affinity_masks);
+		vp_dev->msix_affinity_masks = NULL;
+	}
 
-	if (vp_dev->msix_enabled) {
-		/* Disable the vector used for configuration */
+	/* Disable the vector used for configuration */
+	if (vp_dev->pci_dev->msix_enabled)
 		vp_dev->config_vector(vp_dev, VIRTIO_MSI_NO_VECTOR);
 
-		pci_free_irq_vectors(vp_dev->pci_dev);
-		vp_dev->msix_enabled = 0;
-	}
+	pci_free_irq_vectors(vp_dev->pci_dev);
+	vp_dev->irq_vectors = 0;
 
-	vp_dev->msix_vectors = 0;
-	vp_dev->msix_used_vectors = 0;
 	kfree(vp_dev->msix_names);
 	vp_dev->msix_names = NULL;
-	kfree(vp_dev->msix_affinity_masks);
-	vp_dev->msix_affinity_masks = NULL;
+
 	kfree(vp_dev->vqs);
 	vp_dev->vqs = NULL;
 }
@@ -260,7 +248,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev,
unsigned nvqs,
 		const char * const names[])
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-	int i, err, nvectors = 1, allocated_vectors;
+	int i, err, nvectors = 1;
 	u16 msix_vec;
 
 	vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
@@ -275,15 +263,13 @@ static int vp_find_vqs_msix(struct virtio_device *vdev,
unsigned nvqs,
 	if (err)
 		goto out_del_vqs;
 
-	vp_dev->per_vq_vectors = true;
-	allocated_vectors = vp_dev->msix_used_vectors;
 	for (i = 0; i < nvqs; ++i) {
 		if (!names[i])
 			continue;
 		if (!callbacks[i])
 			msix_vec = VIRTIO_MSI_NO_VECTOR;
 		else
-			msix_vec = allocated_vectors++;
+			msix_vec = vp_dev->irq_vectors++;
 
 		vqs[i] = vp_setup_vq(vdev, i, callbacks[i], names[i], msix_vec);
 		if (IS_ERR(vqs[i])) {
@@ -319,12 +305,11 @@ static int vp_find_vqs_msix_shared(struct virtio_device
*vdev, unsigned nvqs,
 	err = vp_setup_msix_vectors(vdev, 2);
 	if (err)
 		goto out_del_vqs;
-	err = vp_request_msix_vector(vp_dev, vp_dev->msix_used_vectors++,
+	err = vp_request_msix_vector(vp_dev, vp_dev->irq_vectors++,
 			vp_vring_interrupt, "virtqueues", vp_dev);
 	if (err)
 		goto out_del_vqs;
 
-	vp_dev->per_vq_vectors = false;
 	for (i = 0; i < nvqs; ++i) {
 		if (!names[i])
 			continue;
@@ -358,9 +343,8 @@ static int vp_find_vqs_intx(struct virtio_device *vdev,
unsigned nvqs,
 			dev_name(&vdev->dev), vp_dev);
 	if (err)
 		goto out_del_vqs;
+	vp_dev->irq_vectors = 1;
 
-	vp_dev->intx_enabled = 1;
-	vp_dev->per_vq_vectors = false;
 	for (i = 0; i < nvqs; ++i) {
 		if (!names[i]) {
 			vqs[i] = NULL;
@@ -423,7 +407,7 @@ int vp_set_vq_affinity(struct virtqueue *vq, int cpu)
 	if (!vq->callback)
 		return -EINVAL;
 
-	if (vp_dev->msix_enabled) {
+	if (vp_dev->pci_dev->msix_enabled) {
 		mask = vp_dev->msix_affinity_masks[info->msix_vector];
 		irq = pci_irq_vector(vp_dev->pci_dev, info->msix_vector);
 		if (cpu == -1)
diff --git a/drivers/virtio/virtio_pci_common.h
b/drivers/virtio/virtio_pci_common.h
index b2f6662..d3e3a1b 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -82,20 +82,12 @@ struct virtio_pci_device {
 	/* array of all queues for house-keeping */
 	struct virtio_pci_vq_info **vqs;
 
-	/* MSI-X support */
-	int msix_enabled;
-	int intx_enabled;
 	cpumask_var_t *msix_affinity_masks;
 	/* Name strings for interrupts. This size should be enough,
 	 * and I'm too lazy to allocate each name separately. */
 	char (*msix_names)[256];
-	/* Number of available vectors */
-	unsigned msix_vectors;
-	/* Vectors allocated, excluding per-vq vectors if any */
-	unsigned msix_used_vectors;
-
-	/* Whether we have vector per vq */
-	bool per_vq_vectors;
+	/* Total number of interrupt vectors (INTx or MSI-X) */
+	unsigned irq_vectors;
 
 	struct virtqueue *(*setup_vq)(struct virtio_pci_device *vp_dev,
 				      struct virtio_pci_vq_info *info,
diff --git a/drivers/virtio/virtio_pci_legacy.c
b/drivers/virtio/virtio_pci_legacy.c
index 8c4e617..25f90f0 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -169,7 +169,7 @@ static void del_vq(struct virtio_pci_vq_info *info)
 
 	iowrite16(vq->index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
 
-	if (vp_dev->msix_enabled) {
+	if (vp_dev->pci_dev->msix_enabled) {
 		iowrite16(VIRTIO_MSI_NO_VECTOR,
 			  vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
 		/* Flush the write out to device */
diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
index e76bd91..e18d0b0 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -416,7 +416,7 @@ static void del_vq(struct virtio_pci_vq_info *info)
 
 	vp_iowrite16(vq->index, &vp_dev->common->queue_select);
 
-	if (vp_dev->msix_enabled) {
+	if (vp_dev->pci_dev->msix_enabled) {
 		vp_iowrite16(VIRTIO_MSI_NO_VECTOR,
 			     &vp_dev->common->queue_msix_vector);
 		/* Flush the write out to device */
diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
index 90007a1..15b4385 100644
--- a/include/uapi/linux/virtio_pci.h
+++ b/include/uapi/linux/virtio_pci.h
@@ -79,7 +79,7 @@
  * configuration space */
 #define VIRTIO_PCI_CONFIG_OFF(msix_enabled)	((msix_enabled) ? 24 : 20)
 /* Deprecated: please use VIRTIO_PCI_CONFIG_OFF instead */
-#define VIRTIO_PCI_CONFIG(dev)	VIRTIO_PCI_CONFIG_OFF((dev)->msix_enabled)
+#define VIRTIO_PCI_CONFIG(dev)
VIRTIO_PCI_CONFIG_OFF((dev)->pci_dev->msix_enabled)
 
 /* Virtio ABI version, this must match exactly */
 #define VIRTIO_PCI_ABI_VERSION		0
-- 
2.1.4

FYI, I've got an updated version of this series that I will send
out together with the affinity patches once a prep patch makes it
to the tip tree.  Feel free to ignore this version for now.