virtio_pci: minor MSI-X cleanups

1) Rename vp_request_vectors to vp_request_msix_vectors, and take
   non-MSI-X case out to caller.
2) Comment weird pci_enable_msix API
3) Rename vp_find_vq to setup_vq.
4) Fix spaces to tabs
5) Make nvectors calc internal to vp_try_to_find_vqs()
6) Rename vector to msix_vector for more clarity.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>

diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 248e00e..4a1f1eb 100644 (file)
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -84,7 +84,7 @@ struct virtio_pci_vq_info
        struct list_head node;
 
        /* MSI-X vector (or none) */
-       unsigned vector;
+       unsigned msix_vector;
 };
 
 /* Qumranet donated their vendor ID for devices 0x1000 thru 0x10FF. */
@@ -280,25 +280,14 @@ static void vp_free_vectors(struct virtio_device *vdev)
        vp_dev->msix_entries = NULL;
 }
 
-static int vp_request_vectors(struct virtio_device *vdev, int nvectors,
-                             bool per_vq_vectors)
+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;
 
-       if (!nvectors) {
-               /* Can't allocate MSI-X vectors, use regular interrupt */
-               vp_dev->msix_vectors = 0;
-               err = request_irq(vp_dev->pci_dev->irq, vp_interrupt,
-                                 IRQF_SHARED, name, vp_dev);
-               if (err)
-                       return err;
-               vp_dev->intx_enabled = 1;
-               return 0;
-       }
-
        vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries,
                                       GFP_KERNEL);
        if (!vp_dev->msix_entries)
@@ -311,6 +300,7 @@ static int vp_request_vectors(struct virtio_device *vdev, int nvectors,
        for (i = 0; i < nvectors; ++i)
                vp_dev->msix_entries[i].entry = i;
 
+       /* pci_enable_msix returns positive if we can't get this many. */
        err = pci_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries, nvectors);
        if (err > 0)
                err = -ENOSPC;
@@ -356,10 +346,22 @@ error:
        return err;
 }
 
-static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
-                                   void (*callback)(struct virtqueue *vq),
-                                   const char *name,
-                                   u16 vector)
+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 *setup_vq(struct virtio_device *vdev, unsigned index,
+                                 void (*callback)(struct virtqueue *vq),
+                                 const char *name,
+                                 u16 msix_vec)
 {
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        struct virtio_pci_vq_info *info;
@@ -384,7 +386,7 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
 
        info->queue_index = index;
        info->num = num;
-       info->vector = vector;
+       info->msix_vector = msix_vec;
 
        size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
        info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
@@ -408,10 +410,10 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
        vq->priv = info;
        info->vq = vq;
 
-        if (vector != VIRTIO_MSI_NO_VECTOR) {
-               iowrite16(vector, vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
-               vector = ioread16(vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
-               if (vector == VIRTIO_MSI_NO_VECTOR) {
+       if (msix_vec != VIRTIO_MSI_NO_VECTOR) {
+               iowrite16(msix_vec, vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
+               msix_vec = ioread16(vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
+               if (msix_vec == VIRTIO_MSI_NO_VECTOR) {
                        err = -EBUSY;
                        goto out_assign;
                }
@@ -472,7 +474,8 @@ static void vp_del_vqs(struct virtio_device *vdev)
        list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
                info = vq->priv;
                if (vp_dev->per_vq_vectors)
-                       free_irq(vp_dev->msix_entries[info->vector].vector, vq);
+                       free_irq(vp_dev->msix_entries[info->msix_vector].vector,
+                                vq);
                vp_del_vq(vq);
        }
        vp_dev->per_vq_vectors = false;
@@ -484,38 +487,58 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
                              struct virtqueue *vqs[],
                              vq_callback_t *callbacks[],
                              const char *names[],
-                             int nvectors,
+                             bool use_msix,
                              bool per_vq_vectors)
 {
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-       u16 vector;
-       int i, err, allocated_vectors;
+       u16 msix_vec;
+       int i, err, nvectors, allocated_vectors;
 
-       err = vp_request_vectors(vdev, nvectors, per_vq_vectors);
-       if (err)
-               goto error_request;
+       if (!use_msix) {
+               /* Old style: one normal interrupt for change and all vqs. */
+               err = vp_request_intx(vdev);
+               if (err)
+                       goto error_request;
+       } 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_request;
+       }
 
        vp_dev->per_vq_vectors = per_vq_vectors;
        allocated_vectors = vp_dev->msix_used_vectors;
        for (i = 0; i < nvqs; ++i) {
                if (!callbacks[i] || !vp_dev->msix_enabled)
-                       vector = VIRTIO_MSI_NO_VECTOR;
+                       msix_vec = VIRTIO_MSI_NO_VECTOR;
                else if (vp_dev->per_vq_vectors)
-                       vector = allocated_vectors++;
+                       msix_vec = allocated_vectors++;
                else
-                       vector = VP_MSIX_VQ_VECTOR;
-               vqs[i] = vp_find_vq(vdev, i, callbacks[i], names[i], vector);
+                       msix_vec = VP_MSIX_VQ_VECTOR;
+               vqs[i] = setup_vq(vdev, i, callbacks[i], names[i], msix_vec);
                if (IS_ERR(vqs[i])) {
                        err = PTR_ERR(vqs[i]);
                        goto error_find;
                }
                /* allocate per-vq irq if available and necessary */
-               if (vp_dev->per_vq_vectors && vector != VIRTIO_MSI_NO_VECTOR) {
-                       snprintf(vp_dev->msix_names[vector], sizeof *vp_dev->msix_names,
-                                "%s-%s", dev_name(&vp_dev->vdev.dev), names[i]);
-                       err = request_irq(vp_dev->msix_entries[vector].vector,
-                                         vring_interrupt, 0,
-                                         vp_dev->msix_names[vector], vqs[i]);
+               if (vp_dev->per_vq_vectors) {
+                       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(msix_vec, vring_interrupt, 0,
+                                         vp_dev->msix_names[msix_vec],
+                                         vqs[i]);
                        if (err) {
                                vp_del_vq(vqs[i]);
                                goto error_find;
@@ -537,28 +560,20 @@ static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
                       vq_callback_t *callbacks[],
                       const char *names[])
 {
-       int vectors = 0;
-       int i, uninitialized_var(err);
-
-       /* How many vectors would we like? */
-       for (i = 0; i < nvqs; ++i)
-               if (callbacks[i])
-                       ++vectors;
+       int err;
 
-       /* We want at most one vector per queue and one for config changes. */
-       err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
-                                vectors + 1, true);
+       /* Try MSI-X with one vector per queue. */
+       err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, true, true);
        if (!err)
                return 0;
-       /* Fallback to separate vectors for config and a shared for queues. */
+       /* Fallback: MSI-X with one vector for config, one shared for queues. */
        err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
-                                2, false);
+                                true, false);
        if (!err)
                return 0;
        /* Finally fall back to regular interrupts. */
-       err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
-                                0, false);
-       return err;
+       return vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
+                                 false, false);
 }
 
 static struct virtio_config_ops virtio_pci_config_ops = {