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Date: Tue, 8 May 2012 14:34:01 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH untested] virtio: allocate extra memory before the ring (
was Re: [RFC PATCH] virtio_console: link vq to port with a private) pointer
in struct virtqueue
> virtio: allocate extra memory before the ring
>
> This let transports put their data inline instead
> of indirect acces through priv pointer.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
And transports would do something like the below to avoid
using priv. Warning: completely untested.
------------------------------>
virtio_pci: put vq info structure inline
vq->priv is now unused by virtio_pci.
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 3c3eea9..4092006 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -73,9 +73,6 @@ enum {
struct virtio_pci_vq_info
{
- /* the actual virtqueue */
- struct virtqueue *vq;
-
/* the number of entries in the queue */
int num;
@@ -90,8 +87,15 @@ struct virtio_pci_vq_info
/* MSI-X vector (or none) */
unsigned msix_vector;
+
+ /* the actual virtqueue. Note: must be the last field */
+ struct virtqueue vq;
};
+#define to_vpinfo(vq) container_of(info, struct virtio_pci_vq_info, vq)
+/* How much space we need to reserve before struct virtqueue */
+#define VPINFO_PRIV offsetof(struct virtio_pci_vq_info, vq)
+
/* Qumranet donated their vendor ID for devices 0x1000 thru 0x10FF. */
static struct pci_device_id virtio_pci_id_table[] = {
{ 0x1af4, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
@@ -202,7 +206,7 @@ static void vp_reset(struct virtio_device *vdev)
static void vp_notify(struct virtqueue *vq)
{
struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
- struct virtio_pci_vq_info *info = vq->priv;
+ struct virtio_pci_vq_info *info = to_vpinfo(vq);
/* we write the queue's selector into the notification register to
* signal the other end */
@@ -232,7 +236,7 @@ static irqreturn_t vp_vring_interrupt(int irq, void *opaque)
spin_lock_irqsave(&vp_dev->lock, flags);
list_for_each_entry(info, &vp_dev->virtqueues, node) {
- if (vring_interrupt(irq, info->vq) == IRQ_HANDLED)
+ if (vring_interrupt(irq, &info->vq) == IRQ_HANDLED)
ret = IRQ_HANDLED;
}
spin_unlock_irqrestore(&vp_dev->lock, flags);
@@ -385,6 +389,7 @@ static struct virtqueue *setup_vq(struct virtio_device *vdev, unsigned index,
struct virtio_pci_vq_info *info;
struct virtqueue *vq;
unsigned long flags, size;
+ void *queue;
u16 num;
int err;
@@ -398,35 +403,34 @@ static struct virtqueue *setup_vq(struct virtio_device *vdev, unsigned index,
/* allocate and fill out our structure the represents an active
* queue */
- info = kmalloc(sizeof(struct virtio_pci_vq_info), GFP_KERNEL);
- if (!info)
- return ERR_PTR(-ENOMEM);
-
- info->queue_index = index;
- info->num = num;
- 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);
- if (info->queue == NULL) {
+ queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
+ if (queue == NULL) {
err = -ENOMEM;
goto out_info;
}
/* activate the queue */
- iowrite32(virt_to_phys(info->queue) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
+ iowrite32(virt_to_phys(queue) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
- /* create the vring */
- vq = vring_new_virtqueue(0, info->num, VIRTIO_PCI_VRING_ALIGN, vdev,
- true, info->queue, vp_notify, callback, name);
+ /* We can store transport specific data before the vq field.
+ * Make sure we don't have any fields after it. */
+ BUILD_BUG_ON(VPINFO_PRIV + sizeof info->vq != sizeof *info);
+
+ vq = vring_new_virtqueue(VPINFO_PRIV, num, VIRTIO_PCI_VRING_ALIGN, vdev,
+ true, queue, vp_notify, callback, name);
if (!vq) {
err = -ENOMEM;
goto out_activate_queue;
}
- vq->priv = info;
- info->vq = vq;
+ info = to_vpinfo(vq);
+
+ info->queue_index = index;
+ info->num = num;
+ info->msix_vector = msix_vec;
if (msix_vec != VIRTIO_MSI_NO_VECTOR) {
iowrite16(msix_vec, vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
@@ -448,20 +452,21 @@ static struct virtqueue *setup_vq(struct virtio_device *vdev, unsigned index,
return vq;
out_assign:
- vring_del_virtqueue(vq, 0);
+ vring_del_virtqueue(vq, VPINFO_PRIV);
out_activate_queue:
iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
free_pages_exact(info->queue, size);
out_info:
- kfree(info);
return ERR_PTR(err);
}
static void vp_del_vq(struct virtqueue *vq)
{
struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
- struct virtio_pci_vq_info *info = vq->priv;
+ struct virtio_pci_vq_info *info = to_vpinfo(vq);
unsigned long flags, size;
+ void *queue = info->queue;
+ u16 num = info->num;
spin_lock_irqsave(&vp_dev->lock, flags);
list_del(&info->node);
@@ -476,14 +481,13 @@ static void vp_del_vq(struct virtqueue *vq)
ioread8(vp_dev->ioaddr + VIRTIO_PCI_ISR);
}
- vring_del_virtqueue(vq, 0);
+ vring_del_virtqueue(vq, VPINFO_PRIV);
/* Select and deactivate the queue */
iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
size = PAGE_ALIGN(vring_size(info->num, VIRTIO_PCI_VRING_ALIGN));
- free_pages_exact(info->queue, size);
- kfree(info);
+ free_pages_exact(queue, size);
}
/* the config->del_vqs() implementation */
@@ -494,7 +498,7 @@ static void vp_del_vqs(struct virtio_device *vdev)
struct virtio_pci_vq_info *info;
list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
- info = vq->priv;
+ info = to_vpinfo(vq);
if (vp_dev->per_vq_vectors &&
info->msix_vector != VIRTIO_MSI_NO_VECTOR)
free_irq(vp_dev->msix_entries[info->msix_vector].vector,
--
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