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SubjectRe: [RFC PATCH] virtio-mmio: support for multiple irqs
On 2014/11/6 17:34, Michael S. Tsirkin wrote:
> On Tue, Nov 04, 2014 at 05:35:12PM +0800, Shannon Zhao wrote:
>> As the current virtio-mmio only support single irq,
>> so some advanced features such as vhost-net with irqfd
>> are not supported. And the net performance is not
>> the best without vhost-net and irqfd supporting.
>>
>> This patch support virtio-mmio to request multiple
>> irqs like virtio-pci. With this patch and qemu assigning
>> multiple irqs for virtio-mmio device, it's ok to use
>> vhost-net with irqfd on arm/arm64.
>>
>> As arm doesn't support msi-x now, we use GSI for
>> multiple irq. In this patch we use "vm_try_to_find_vqs"
>> to check whether multiple irqs are supported like
>> virtio-pci.
>>
>> Is this the right direction? is there other ways to
>> make virtio-mmio support multiple irq? Hope for feedback.
>> Thanks.
>>
>> Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
>
>
> So how does guest discover whether host device supports multiple IRQs?

Guest uses vm_try_to_find_vqs to check whether it can get multiple IRQs
like virtio-pci uses vp_try_to_find_vqs. And within function
vm_request_multiple_irqs, guest check whether the number of IRQs host
device gives is equal to the number we want.

for (i = 0; i < nirqs; i++) {
irq = platform_get_irq(vm_dev->pdev, i);
if (irq == -ENXIO)
goto error;
}

If we can't get the expected number of IRQs, return error and this try
fails. Then guest will try two IRQS and single IRQ like virtio-pci.

> Could you please document the new interface?
> E.g. send a patch for virtio spec.

Ok, I'll send it later. Thank you very much :)

Shannon

> I think this really should be controlled by hypervisor, per device.
> I'm also tempted to make this a virtio 1.0 only feature.
>
>
>
>> ---
>> drivers/virtio/virtio_mmio.c | 234 ++++++++++++++++++++++++++++++++++++------
>> 1 files changed, 203 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
>> index c600ccf..2b7d935 100644
>> --- a/drivers/virtio/virtio_mmio.c
>> +++ b/drivers/virtio/virtio_mmio.c
>> @@ -122,6 +122,15 @@ struct virtio_mmio_device {
>> /* a list of queues so we can dispatch IRQs */
>> spinlock_t lock;
>> struct list_head virtqueues;
>> +
>> + /* multiple irq support */
>> + int single_irq_enabled;
>> + /* Number of available irqs */
>> + unsigned num_irqs;
>> + /* Used number of irqs */
>> + int used_irqs;
>> + /* Name strings for interrupts. */
>> + char (*vm_vq_names)[256];
>> };
>>
>> struct virtio_mmio_vq_info {
>> @@ -229,33 +238,53 @@ static bool vm_notify(struct virtqueue *vq)
>> return true;
>> }
>>
>> +/* Handle a configuration change: Tell driver if it wants to know. */
>> +static irqreturn_t vm_config_changed(int irq, void *opaque)
>> +{
>> + struct virtio_mmio_device *vm_dev = opaque;
>> + struct virtio_driver *vdrv = container_of(vm_dev->vdev.dev.driver,
>> + struct virtio_driver, driver);
>> +
>> + if (vdrv && vdrv->config_changed)
>> + vdrv->config_changed(&vm_dev->vdev);
>> + return IRQ_HANDLED;
>> +}
>> +
>> /* Notify all virtqueues on an interrupt. */
>> -static irqreturn_t vm_interrupt(int irq, void *opaque)
>> +static irqreturn_t vm_vring_interrupt(int irq, void *opaque)
>> {
>> struct virtio_mmio_device *vm_dev = opaque;
>> struct virtio_mmio_vq_info *info;
>> - struct virtio_driver *vdrv = container_of(vm_dev->vdev.dev.driver,
>> - struct virtio_driver, driver);
>> - unsigned long status;
>> + irqreturn_t ret = IRQ_NONE;
>> unsigned long flags;
>> +
>> + spin_lock_irqsave(&vm_dev->lock, flags);
>> + list_for_each_entry(info, &vm_dev->virtqueues, node) {
>> + if (vring_interrupt(irq, info->vq) == IRQ_HANDLED)
>> + ret = IRQ_HANDLED;
>> + }
>> + spin_unlock_irqrestore(&vm_dev->lock, flags);
>> +
>> + return ret;
>> +}
>> +
>> +/* Notify all virtqueues and handle a configuration
>> + * change on an interrupt. */
>> +static irqreturn_t vm_interrupt(int irq, void *opaque)
>> +{
>> + struct virtio_mmio_device *vm_dev = opaque;
>> + unsigned long status;
>> irqreturn_t ret = IRQ_NONE;
>>
>> /* Read and acknowledge interrupts */
>> status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS);
>> writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK);
>>
>> - if (unlikely(status & VIRTIO_MMIO_INT_CONFIG)
>> - && vdrv && vdrv->config_changed) {
>> - vdrv->config_changed(&vm_dev->vdev);
>> - ret = IRQ_HANDLED;
>> - }
>> + if (unlikely(status & VIRTIO_MMIO_INT_CONFIG))
>> + return vm_config_changed(irq, opaque);
>>
>> - if (likely(status & VIRTIO_MMIO_INT_VRING)) {
>> - spin_lock_irqsave(&vm_dev->lock, flags);
>> - list_for_each_entry(info, &vm_dev->virtqueues, node)
>> - ret |= vring_interrupt(irq, info->vq);
>> - spin_unlock_irqrestore(&vm_dev->lock, flags);
>> - }
>> + if (likely(status & VIRTIO_MMIO_INT_VRING))
>> + return vm_vring_interrupt(irq, opaque);
>>
>> return ret;
>> }
>> @@ -284,18 +313,98 @@ static void vm_del_vq(struct virtqueue *vq)
>> kfree(info);
>> }
>>
>> -static void vm_del_vqs(struct virtio_device *vdev)
>> +static void vm_free_irqs(struct virtio_device *vdev)
>> {
>> + int i;
>> struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
>> +
>> + if (vm_dev->single_irq_enabled) {
>> + free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
>> + vm_dev->single_irq_enabled = 0;
>> + }
>> +
>> + for (i = 0; i < vm_dev->used_irqs; ++i)
>> + free_irq(platform_get_irq(vm_dev->pdev, i), vm_dev);
>> +
>> + vm_dev->num_irqs = 0;
>> + vm_dev->used_irqs = 0;
>> + kfree(vm_dev->vm_vq_names);
>> + vm_dev->vm_vq_names = NULL;
>> +}
>> +
>> +static void vm_del_vqs(struct virtio_device *vdev)
>> +{
>> struct virtqueue *vq, *n;
>>
>> list_for_each_entry_safe(vq, n, &vdev->vqs, list)
>> vm_del_vq(vq);
>>
>> - free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
>> + vm_free_irqs(vdev);
>> +}
>> +
>> +static int vm_request_multiple_irqs(struct virtio_device *vdev, int nirqs,
>> + bool per_vq_irq)
>> +{
>> + int err = -ENOMEM;
>> + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
>> + unsigned i, v;
>> + int irq = 0;
>> +
>> + vm_dev->num_irqs = nirqs;
>> + vm_dev->used_irqs = 0;
>> +
>> + vm_dev->vm_vq_names = kmalloc_array(nirqs, sizeof(*vm_dev->vm_vq_names),
>> + GFP_KERNEL);
>> + if (!vm_dev->vm_vq_names)
>> + goto error;
>> +
>> + for (i = 0; i < nirqs; i++) {
>> + irq = platform_get_irq(vm_dev->pdev, i);
>> + if (irq == -ENXIO)
>> + goto error;
>> + }
>> +
>> + /* Set the irq used for configuration */
>> + v = vm_dev->used_irqs;
>> + snprintf(vm_dev->vm_vq_names[v], sizeof(*vm_dev->vm_vq_names),
>> + "%s-config", dev_name(&vdev->dev));
>> + irq = platform_get_irq(vm_dev->pdev, v);
>> + err = request_irq(irq, vm_config_changed, 0,
>> + vm_dev->vm_vq_names[v], vm_dev);
>> + ++vm_dev->used_irqs;
>> + if (err)
>> + goto error;
>> +
>> + if (!per_vq_irq) {
>> + /* Shared irq for all VQs */
>> + v = vm_dev->used_irqs;
>> + snprintf(vm_dev->vm_vq_names[v], sizeof(*vm_dev->vm_vq_names),
>> + "%s-virtqueues", dev_name(&vdev->dev));
>> + irq = platform_get_irq(vm_dev->pdev, v);
>> + err = request_irq(irq, vm_vring_interrupt, 0,
>> + vm_dev->vm_vq_names[v], vm_dev);
>> + if (err)
>> + goto error;
>> + ++vm_dev->used_irqs;
>> + }
>> + return 0;
>> +error:
>> + vm_free_irqs(vdev);
>> + return err;
>> }
>>
>> +static int vm_request_single_irq(struct virtio_device *vdev)
>> +{
>> + int err;
>> + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
>> + int irq = platform_get_irq(vm_dev->pdev, 0);
>>
>> + err = request_irq(irq, vm_interrupt, IRQF_SHARED,
>> + dev_name(&vdev->dev), vm_dev);
>> + if (!err)
>> + vm_dev->single_irq_enabled = 1;
>> + return err;
>> +}
>>
>> static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
>> void (*callback)(struct virtqueue *vq),
>> @@ -392,29 +501,92 @@ error_available:
>> return ERR_PTR(err);
>> }
>>
>> -static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
>> - struct virtqueue *vqs[],
>> - vq_callback_t *callbacks[],
>> - const char *names[])
>> +static int vm_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
>> + struct virtqueue *vqs[],
>> + vq_callback_t *callbacks[],
>> + const char *names[],
>> + bool use_multiple_irq,
>> + bool per_vq_irq)
>> {
>> struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
>> - unsigned int irq = platform_get_irq(vm_dev->pdev, 0);
>> - int i, err;
>> + int i, err, nirqs, irq;
>> +
>> + if (!use_multiple_irq) {
>> + /* Old style: one normal interrupt for change and all vqs. */
>> + err = vm_request_single_irq(vdev);
>> + if (err)
>> + goto error_request;
>> + } else {
>> + if (per_vq_irq) {
>> + /* Best option: one for change interrupt, one per vq. */
>> + nirqs = 1;
>> + for (i = 0; i < nvqs; ++i)
>> + if (callbacks[i])
>> + ++nirqs;
>> + } else {
>> + /* Second best: one for change, shared for all vqs. */
>> + nirqs = 2;
>> + }
>>
>> - err = request_irq(irq, vm_interrupt, IRQF_SHARED,
>> - dev_name(&vdev->dev), vm_dev);
>> - if (err)
>> - return err;
>> + err = vm_request_multiple_irqs(vdev, nirqs, per_vq_irq);
>> + if (err)
>> + goto error_request;
>> + }
>>
>> - for (i = 0; i < nvqs; ++i) {
>> + for (i = 0; i < nvqs; i++) {
>> + if (!names[i]) {
>> + vqs[i] = NULL;
>> + continue;
>> + }
>> vqs[i] = vm_setup_vq(vdev, i, callbacks[i], names[i]);
>> if (IS_ERR(vqs[i])) {
>> - vm_del_vqs(vdev);
>> - return PTR_ERR(vqs[i]);
>> + err = PTR_ERR(vqs[i]);
>> + goto error_find;
>> + }
>> + if (!per_vq_irq || !callbacks[i])
>> + continue;
>> + /* allocate per-vq irq if available and necessary */
>> + snprintf(vm_dev->vm_vq_names[vm_dev->used_irqs],
>> + sizeof(*vm_dev->vm_vq_names),
>> + "%s-%s",
>> + dev_name(&vm_dev->vdev.dev), names[i]);
>> + irq = platform_get_irq(vm_dev->pdev, vm_dev->used_irqs);
>> + err = request_irq(irq, vring_interrupt, 0,
>> + vm_dev->vm_vq_names[vm_dev->used_irqs], vqs[i]);
>> + if (err) {
>> + vm_del_vq(vqs[i]);
>> + goto error_find;
>> }
>> + ++vm_dev->used_irqs;
>> }
>> -
>> return 0;
>> +error_find:
>> + vm_del_vqs(vdev);
>> +
>> +error_request:
>> + return err;
>> +}
>> +
>> +static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
>> + struct virtqueue *vqs[],
>> + vq_callback_t *callbacks[],
>> + const char *names[])
>> +{
>> + int err;
>> +
>> + /* Try multiple irqs with one irq per queue. */
>> + err = vm_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, true, true);
>> + if (!err)
>> + return 0;
>> + /* Fallback: multiple irqs with one irq for config,
>> + * one shared for queues. */
>> + err = vm_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
>> + true, false);
>> + if (!err)
>> + return 0;
>> + /* Finally fall back to regular single interrupts. */
>> + return vm_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
>> + false, false);
>> }
>>
>> static const char *vm_bus_name(struct virtio_device *vdev)
>> --
>> 1.7.1
>
> .
>


--
Shannon



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