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Date: Fri, 11 Nov 2011 18:36:15 +0530
From: Krishna Kumar <krkumar2@...ibm.com>
To: rusty@...tcorp.com.au, mst@...hat.com
Cc: netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
davem@...emloft.net, Krishna Kumar <krkumar2@...ibm.com>,
kvm@...r.kernel.org
Subject: [RFC] [ver3 PATCH 5/6] virtio: Implement find_vqs_irq()
Implement find_vqs_irq() to reduce number of vectors. It can
be used to specify which vq's need their own irqs, and which
can share irqs with other vq's.
Signed-off-by: krkumar2@...ibm.com
---
drivers/virtio/virtio_pci.c | 108 ++++++++++++++++++++++++--------
include/linux/virtio_config.h | 14 ++++
2 files changed, 95 insertions(+), 27 deletions(-)
diff -ruNp org/drivers/virtio/virtio_pci.c new/drivers/virtio/virtio_pci.c
--- org/drivers/virtio/virtio_pci.c 2011-11-11 16:45:09.000000000 +0530
+++ new/drivers/virtio/virtio_pci.c 2011-11-11 16:54:35.000000000 +0530
@@ -40,7 +40,7 @@ struct virtio_pci_device
/* the IO mapping for the PCI config space */
void __iomem *ioaddr;
- /* a list of queues so we can dispatch IRQs */
+ /* a list of queues which have registered to receive IRQs */
spinlock_t lock;
struct list_head virtqueues;
@@ -196,7 +196,7 @@ static irqreturn_t vp_config_changed(int
return IRQ_HANDLED;
}
-/* Notify all virtqueues on an interrupt. */
+/* Notify all vq's on 'virtqueues' list on an interrupt. */
static irqreturn_t vp_vring_interrupt(int irq, void *opaque)
{
struct virtio_pci_device *vp_dev = opaque;
@@ -358,7 +358,7 @@ static struct virtqueue *setup_vq(struct
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct virtio_pci_vq_info *info;
struct virtqueue *vq;
- unsigned long flags, size;
+ unsigned long size;
u16 num;
int err;
@@ -378,6 +378,7 @@ static struct virtqueue *setup_vq(struct
info->num = num;
info->msix_vector = msix_vec;
+ INIT_LIST_HEAD(&info->node);
size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
@@ -411,14 +412,6 @@ static struct virtqueue *setup_vq(struct
}
}
- if (callback) {
- spin_lock_irqsave(&vp_dev->lock, flags);
- list_add(&info->node, &vp_dev->virtqueues);
- spin_unlock_irqrestore(&vp_dev->lock, flags);
- } else {
- INIT_LIST_HEAD(&info->node);
- }
-
return vq;
out_assign:
@@ -472,7 +465,8 @@ static void vp_del_vqs(struct virtio_dev
if (vp_dev->per_vq_vectors &&
info->msix_vector != VIRTIO_MSI_NO_VECTOR)
free_irq(vp_dev->msix_entries[info->msix_vector].vector,
- vq);
+ list_empty(&info->node) ?
+ (void *)vq : (void *)vp_dev);
vp_del_vq(vq);
}
vp_dev->per_vq_vectors = false;
@@ -480,16 +474,37 @@ static void vp_del_vqs(struct virtio_dev
vp_free_vectors(vdev);
}
+static void add_vq_to_list(struct virtqueue *vq,
+ struct virtio_pci_device *vp_dev,
+ vq_callback_t *cb)
+{
+ struct virtio_pci_vq_info *info = vq->priv;
+ unsigned long flags;
+
+ if (cb) {
+ spin_lock_irqsave(&vp_dev->lock, flags);
+ list_add(&info->node, &vp_dev->virtqueues);
+ spin_unlock_irqrestore(&vp_dev->lock, flags);
+ }
+}
+
+/* Return true if flags is NULL, or 'bit'# in flags is clear */
+static bool bit_clear(unsigned long *flags, int bit)
+{
+ return flags ? !test_bit(bit, flags) : true;
+}
+
static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
const char *names[],
bool use_msix,
- bool per_vq_vectors)
+ bool per_vq_vectors, unsigned long *flags)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
u16 msix_vec;
int i, err, nvectors, allocated_vectors;
+ int count = 0; /* Count of vq's using shared irq's */
if (!use_msix) {
/* Old style: one normal interrupt for change and all vqs. */
@@ -500,9 +515,19 @@ static int vp_try_to_find_vqs(struct vir
if (per_vq_vectors) {
/* Best option: one for change interrupt, one per vq. */
nvectors = 1;
- for (i = 0; i < nvqs; ++i)
- if (callbacks[i])
+ for (i = 0; i < nvqs; ++i) {
+ bool alloc_irq = bit_clear(flags, i);
+
+ /*
+ * We allocate a vector if cb is present,
+ * AND (driver requested a vector OR this
+ * is the first shared vector).
+ */
+ if (callbacks[i] &&
+ (alloc_irq || ++count == 1))
++nvectors;
+ }
+ count = 0;
} else {
/* Second best: one for change, shared for all vqs. */
nvectors = 2;
@@ -516,20 +541,38 @@ static int vp_try_to_find_vqs(struct vir
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)
+ bool alloc_irq = bit_clear(flags, i);
+ irq_handler_t irq_handler;
+ void *data;
+
+ if (!callbacks[i] || !vp_dev->msix_enabled ||
+ !(alloc_irq || ++count == 1))
msix_vec = VIRTIO_MSI_NO_VECTOR;
else if (vp_dev->per_vq_vectors)
msix_vec = allocated_vectors++;
else
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;
}
- if (!vp_dev->per_vq_vectors || msix_vec == VIRTIO_MSI_NO_VECTOR)
+ if (!vp_dev->per_vq_vectors ||
+ msix_vec == VIRTIO_MSI_NO_VECTOR) {
+ add_vq_to_list(vqs[i], vp_dev, callbacks[i]);
continue;
+ }
+
+ if (alloc_irq) {
+ irq_handler = vring_interrupt;
+ data = vqs[i];
+ } else {
+ add_vq_to_list(vqs[i], vp_dev, callbacks[i]);
+ irq_handler = vp_vring_interrupt;
+ data = vp_dev;
+ }
/* allocate per-vq irq if available and necessary */
snprintf(vp_dev->msix_names[msix_vec],
@@ -537,9 +580,9 @@ static int vp_try_to_find_vqs(struct vir
"%s-%s",
dev_name(&vp_dev->vdev.dev), names[i]);
err = request_irq(vp_dev->msix_entries[msix_vec].vector,
- vring_interrupt, 0,
+ irq_handler, 0,
vp_dev->msix_names[msix_vec],
- vqs[i]);
+ data);
if (err) {
vp_del_vq(vqs[i]);
goto error_find;
@@ -554,26 +597,36 @@ error_request:
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[])
+/* the config->find_vqs_irq() implementation */
+static int vp_find_vqs_irq(struct virtio_device *vdev, unsigned nvqs,
+ struct virtqueue *vqs[],
+ vq_callback_t *callbacks[],
+ const char *names[], unsigned long *flags)
{
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, true,
+ flags);
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);
+ true, false, NULL);
if (!err)
return 0;
/* Finally fall back to regular interrupts. */
return vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
- false, false);
+ false, false, NULL);
+}
+
+/* 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[])
+{
+ return vp_find_vqs_irq(vdev, nvqs, vqs, callbacks, names, NULL);
}
static struct virtio_config_ops virtio_pci_config_ops = {
@@ -583,6 +636,7 @@ static struct virtio_config_ops virtio_p
.set_status = vp_set_status,
.reset = vp_reset,
.find_vqs = vp_find_vqs,
+ .find_vqs_irq = vp_find_vqs_irq,
.del_vqs = vp_del_vqs,
.get_features = vp_get_features,
.finalize_features = vp_finalize_features,
diff -ruNp org/include/linux/virtio_config.h new/include/linux/virtio_config.h
--- org/include/linux/virtio_config.h 2011-11-11 16:45:09.000000000 +0530
+++ new/include/linux/virtio_config.h 2011-11-11 16:45:21.000000000 +0530
@@ -92,6 +92,16 @@
* callbacks: array of callbacks, for each virtqueue
* names: array of virtqueue names (mainly for debugging)
* Returns 0 on success or error status
+ * @find_vqs_irq: find virtqueues and instantiate them. The flags parameter
+ * indicates the vq's that can share irq's.
+ * vdev: the virtio_device
+ * nvqs: the number of virtqueues to find
+ * vqs: on success, includes new virtqueues
+ * callbacks: array of callbacks, for each virtqueue
+ * names: array of virtqueue names (mainly for debugging)
+ * flags: indicates which vq's need their own irq and which can share.
+ * See example usage in virtio_net.c
+ * Returns 0 on success or error status
* @del_vqs: free virtqueues found by find_vqs().
* @get_features: get the array of feature bits for this device.
* vdev: the virtio_device
@@ -114,6 +124,10 @@ struct virtio_config_ops {
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
const char *names[]);
+ int (*find_vqs_irq)(struct virtio_device *vdev, unsigned nvqs,
+ struct virtqueue *vqs[],
+ vq_callback_t *callbacks[],
+ const char *names[], unsigned long *flags);
void (*del_vqs)(struct virtio_device *);
u32 (*get_features)(struct virtio_device *vdev);
void (*finalize_features)(struct virtio_device *vdev);
--
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