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virtio: refactor find_vqs
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This refactors find_vqs, making it more readable and robust, and fixing
two regressions from 2.6.30:
- double free_irq causing BUG_ON on device removal
- probe failure when vq can't be assigned to msi-x vector
  (reported on old host kernels)

Tested-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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@mstsirkin @rustyrussell
mstsirkin authored and rustyrussell committed Jul 30, 2009
1 parent f6c8250 commit e969fed
Showing 1 changed file with 119 additions and 93 deletions.
212 changes: 119 additions & 93 deletions drivers/virtio/virtio_pci.c
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,10 @@ struct virtio_pci_device
char (*msix_names)[256];
/* Number of available vectors */
unsigned msix_vectors;
/* Vectors allocated */
/* Vectors allocated, excluding per-vq vectors if any */
unsigned msix_used_vectors;
/* Whether we have vector per vq */
bool per_vq_vectors;
};

/* Constants for MSI-X */
Expand Down Expand Up @@ -278,27 +280,24 @@ static void vp_free_vectors(struct virtio_device *vdev)
vp_dev->msix_entries = NULL;
}

static int vp_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
int *options, int noptions)
{
int i;
for (i = 0; i < noptions; ++i)
if (!pci_enable_msix(dev, entries, options[i]))
return options[i];
return -EBUSY;
}

static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs)
static int vp_request_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;
/* We want at most one vector per queue and one for config changes.
* Fallback to separate vectors for config and a shared for queues.
* Finally fall back to regular interrupts. */
int options[] = { max_vqs + 1, 2 };
int nvectors = max(options[0], options[1]);

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);
Expand All @@ -312,41 +311,34 @@ static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs)
for (i = 0; i < nvectors; ++i)
vp_dev->msix_entries[i].entry = i;

err = vp_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries,
options, ARRAY_SIZE(options));
if (err < 0) {
/* Can't allocate enough 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)
goto error;
vp_dev->intx_enabled = 1;
} else {
vp_dev->msix_vectors = err;
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(vp_dev->msix_entries[v].vector,
vp_config_changed, 0, vp_dev->msix_names[v],
vp_dev);
if (err)
goto error;
++vp_dev->msix_used_vectors;
err = pci_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries, nvectors);
if (err > 0)
err = -ENOSPC;
if (err)
goto error;
vp_dev->msix_vectors = 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(vp_dev->msix_entries[v].vector,
vp_config_changed, 0, vp_dev->msix_names[v],
vp_dev);
if (err)
goto error;
++vp_dev->msix_used_vectors;

iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
/* Verify we had enough resources to assign the vector */
v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
if (v == VIRTIO_MSI_NO_VECTOR) {
err = -EBUSY;
goto error;
}
iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
/* Verify we had enough resources to assign the vector */
v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
if (v == VIRTIO_MSI_NO_VECTOR) {
err = -EBUSY;
goto error;
}

if (vp_dev->msix_vectors && vp_dev->msix_vectors != max_vqs + 1) {
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,
Expand All @@ -366,13 +358,14 @@ static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs)

static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
void (*callback)(struct virtqueue *vq),
const char *name)
const char *name,
u16 vector)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct virtio_pci_vq_info *info;
struct virtqueue *vq;
unsigned long flags, size;
u16 num, vector;
u16 num;
int err;

/* Select the queue we're interested in */
Expand All @@ -391,7 +384,7 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,

info->queue_index = index;
info->num = num;
info->vector = VIRTIO_MSI_NO_VECTOR;
info->vector = vector;

size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
Expand All @@ -415,22 +408,7 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
vq->priv = info;
info->vq = vq;

/* allocate per-vq vector if available and necessary */
if (callback && vp_dev->msix_used_vectors < vp_dev->msix_vectors) {
vector = vp_dev->msix_used_vectors;
snprintf(vp_dev->msix_names[vector], sizeof *vp_dev->msix_names,
"%s-%s", dev_name(&vp_dev->vdev.dev), name);
err = request_irq(vp_dev->msix_entries[vector].vector,
vring_interrupt, 0,
vp_dev->msix_names[vector], vq);
if (err)
goto out_request_irq;
info->vector = vector;
++vp_dev->msix_used_vectors;
} else
vector = VP_MSIX_VQ_VECTOR;

if (callback && vp_dev->msix_enabled) {
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) {
Expand All @@ -446,11 +424,6 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
return vq;

out_assign:
if (info->vector != VIRTIO_MSI_NO_VECTOR) {
free_irq(vp_dev->msix_entries[info->vector].vector, vq);
--vp_dev->msix_used_vectors;
}
out_request_irq:
vring_del_virtqueue(vq);
out_activate_queue:
iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
Expand All @@ -472,9 +445,6 @@ static void vp_del_vq(struct virtqueue *vq)

iowrite16(info->queue_index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);

if (info->vector != VIRTIO_MSI_NO_VECTOR)
free_irq(vp_dev->msix_entries[info->vector].vector, vq);

if (vp_dev->msix_enabled) {
iowrite16(VIRTIO_MSI_NO_VECTOR,
vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
Expand All @@ -495,44 +465,100 @@ static void vp_del_vq(struct virtqueue *vq)
/* the config->del_vqs() implementation */
static 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)
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);
vp_del_vq(vq);
}
vp_dev->per_vq_vectors = false;

vp_free_vectors(vdev);
}

/* the config->find_vqs() implementation */
static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
const char *names[])
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 per_vq_vectors)
{
int vectors = 0;
int i, err;

/* How many vectors would we like? */
for (i = 0; i < nvqs; ++i)
if (callbacks[i])
++vectors;
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
u16 vector;
int i, err, allocated_vectors;

err = vp_request_vectors(vdev, vectors);
err = vp_request_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) {
vqs[i] = vp_find_vq(vdev, i, callbacks[i], names[i]);
if (IS_ERR(vqs[i]))
if (!callbacks[i] || !vp_dev->msix_enabled)
vector = VIRTIO_MSI_NO_VECTOR;
else if (vp_dev->per_vq_vectors)
vector = allocated_vectors++;
else
vector = VP_MSIX_VQ_VECTOR;
vqs[i] = vp_find_vq(vdev, i, callbacks[i], names[i], vector);
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 (err) {
vp_del_vq(vqs[i]);
goto error_find;
}
}
}
return 0;

error_find:
vp_del_vqs(vdev);

error_request:
return PTR_ERR(vqs[i]);
return err;
}

/* the config->find_vqs() implementation */
static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
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;

/* 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);
if (!err)
return 0;
/* Fallback to separate vectors for config and a shared for queues. */
err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
2, 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;
}

static struct virtio_config_ops virtio_pci_config_ops = {
Expand Down

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