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virtio_pci: minor MSI-X cleanups
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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>
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Rusty Russell committed Sep 23, 2009
1 parent ebc79c4 commit f68d240
Showing 1 changed file with 70 additions and 55 deletions.
125 changes: 70 additions & 55 deletions drivers/virtio/virtio_pci.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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. */
Expand Down Expand Up @@ -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)
Expand All @@ -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;
Expand Down Expand Up @@ -356,10 +346,22 @@ static int vp_request_vectors(struct virtio_device *vdev, int nvectors,
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;
Expand All @@ -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);
Expand All @@ -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;
}
Expand Down Expand Up @@ -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;
Expand All @@ -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;
Expand All @@ -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 = {
Expand Down

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