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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Zha Bin <zhabin@linux.alibaba.com>
Cc: linux-kernel@vger.kernel.org, jasowang@redhat.com,
	slp@redhat.com, virtio-dev@lists.oasis-open.org,
	qemu-devel@nongnu.org, gerry@linux.alibaba.com,
	jing2.liu@linux.intel.com, chao.p.peng@linux.intel.com
Subject: Re: [PATCH v2 1/5] virtio-mmio: add notify feature for per-queue
Date: Tue, 11 Feb 2020 05:50:48 -0500	[thread overview]
Message-ID: <20200211055005-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <8a4ea95d6d77a2814aaf6897b5517353289a098e.1581305609.git.zhabin@linux.alibaba.com>

On Mon, Feb 10, 2020 at 05:05:17PM +0800, Zha Bin wrote:
> From: Liu Jiang <gerry@linux.alibaba.com>
> 
> The standard virtio-mmio devices use notification register to signal
> backend. This will cause vmexits and slow down the performance when we
> passthrough the virtio-mmio devices to guest virtual machines.
> We proposed to update virtio over MMIO spec to add the per-queue
> notify feature VIRTIO_F_MMIO_NOTIFICATION[1]. It can allow the VMM to
> configure notify location for each queue.
> 
> [1] https://lkml.org/lkml/2020/1/21/31
> 
> Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>
> Co-developed-by: Zha Bin <zhabin@linux.alibaba.com>
> Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
> Co-developed-by: Jing Liu <jing2.liu@linux.intel.com>
> Signed-off-by: Jing Liu <jing2.liu@linux.intel.com>
> Co-developed-by: Chao Peng <chao.p.peng@linux.intel.com>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>

So this is for pass-through for nested virt?
OK but let's split this out please, and benchmark separately.


> ---
>  drivers/virtio/virtio_mmio.c       | 37 +++++++++++++++++++++++++++++++++++--
>  include/uapi/linux/virtio_config.h |  8 +++++++-
>  2 files changed, 42 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 97d5725..1733ab97 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -90,6 +90,9 @@ struct virtio_mmio_device {
>  	/* a list of queues so we can dispatch IRQs */
>  	spinlock_t lock;
>  	struct list_head virtqueues;
> +
> +	unsigned short notify_base;
> +	unsigned short notify_multiplier;
>  };
>  
>  struct virtio_mmio_vq_info {
> @@ -98,6 +101,9 @@ struct virtio_mmio_vq_info {
>  
>  	/* the list node for the virtqueues list */
>  	struct list_head node;
> +
> +	/* Notify Address*/
> +	unsigned int notify_addr;
>  };
>  
>  
> @@ -119,13 +125,23 @@ static u64 vm_get_features(struct virtio_device *vdev)
>  	return features;
>  }
>  
> +static void vm_transport_features(struct virtio_device *vdev, u64 features)
> +{
> +	if (features & BIT_ULL(VIRTIO_F_MMIO_NOTIFICATION))
> +		__virtio_set_bit(vdev, VIRTIO_F_MMIO_NOTIFICATION);
> +}
> +
>  static int vm_finalize_features(struct virtio_device *vdev)
>  {
>  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> +	u64 features = vdev->features;
>  
>  	/* Give virtio_ring a chance to accept features. */
>  	vring_transport_features(vdev);
>  
> +	/* Give virtio_mmio a chance to accept features. */
> +	vm_transport_features(vdev, features);
> +
>  	/* Make sure there is are no mixed devices */
>  	if (vm_dev->version == 2 &&
>  			!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
> @@ -272,10 +288,13 @@ static void vm_reset(struct virtio_device *vdev)
>  static bool vm_notify(struct virtqueue *vq)
>  {
>  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
> +	struct virtio_mmio_vq_info *info = vq->priv;
>  
> -	/* We write the queue's selector into the notification register to
> +	/* We write the queue's selector into the Notify Address to
>  	 * signal the other end */
> -	writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);
> +	if (info)
> +		writel(vq->index, vm_dev->base + info->notify_addr);
> +
>  	return true;
>  }
>  
> @@ -434,6 +453,12 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
>  	vq->priv = info;
>  	info->vq = vq;
>  
> +	if (__virtio_test_bit(vdev, VIRTIO_F_MMIO_NOTIFICATION))
> +		info->notify_addr = vm_dev->notify_base +
> +				vm_dev->notify_multiplier * vq->index;
> +	else
> +		info->notify_addr = VIRTIO_MMIO_QUEUE_NOTIFY;
> +
>  	spin_lock_irqsave(&vm_dev->lock, flags);
>  	list_add(&info->node, &vm_dev->virtqueues);
>  	spin_unlock_irqrestore(&vm_dev->lock, flags);
> @@ -471,6 +496,14 @@ static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
>  		return irq;
>  	}
>  
> +	if (__virtio_test_bit(vdev, VIRTIO_F_MMIO_NOTIFICATION)) {
> +		unsigned int notify = readl(vm_dev->base +
> +				VIRTIO_MMIO_QUEUE_NOTIFY);
> +
> +		vm_dev->notify_base = notify & 0xffff;
> +		vm_dev->notify_multiplier = (notify >> 16) & 0xffff;
> +	}
> +
>  	err = request_irq(irq, vm_interrupt, IRQF_SHARED,
>  			dev_name(&vdev->dev), vm_dev);
>  	if (err)
> diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> index ff8e7dc..5d93c01 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
> @@ -52,7 +52,7 @@
>   * rest are per-device feature bits.
>   */
>  #define VIRTIO_TRANSPORT_F_START	28
> -#define VIRTIO_TRANSPORT_F_END		38
> +#define VIRTIO_TRANSPORT_F_END		40
>  
>  #ifndef VIRTIO_CONFIG_NO_LEGACY
>  /* Do we get callbacks when the ring is completely used, even if we've
> @@ -88,4 +88,10 @@
>   * Does the device support Single Root I/O Virtualization?
>   */
>  #define VIRTIO_F_SR_IOV			37
> +
> +/*
> + * This feature indicates the enhanced notification support on MMIO transport
> + * layer.
> + */
> +#define VIRTIO_F_MMIO_NOTIFICATION	39
>  #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
> -- 
> 1.8.3.1


  reply	other threads:[~2020-02-11 10:51 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10  9:05 [PATCH v2 0/5] virtio mmio specification enhancement Zha Bin
2020-02-10  9:05 ` [PATCH v2 1/5] virtio-mmio: add notify feature for per-queue Zha Bin
2020-02-11 10:50   ` Michael S. Tsirkin [this message]
2020-02-11 11:33   ` Michael S. Tsirkin
2020-02-12  3:39     ` Jason Wang
2020-02-12  8:18       ` Michael S. Tsirkin
2020-02-12  8:53         ` Jason Wang
2020-02-12  9:33           ` Jason Wang
2020-02-12  9:55             ` Michael S. Tsirkin
2020-02-13  3:38               ` Jason Wang
2020-02-10  9:05 ` [PATCH v2 2/5] virtio-mmio: refactor common functionality Zha Bin
2020-02-11 11:19   ` Michael S. Tsirkin
2020-02-12  2:58     ` [virtio-dev] " Liu, Jing2
2020-02-12  7:29       ` Michael S. Tsirkin
2020-02-10  9:05 ` [PATCH v2 3/5] virtio-mmio: create a generic MSI irq domain Zha Bin
2020-02-11 11:16   ` Michael S. Tsirkin
2020-02-12  7:40   ` Michael S. Tsirkin
2020-02-10  9:05 ` [PATCH v2 4/5] virtio-mmio: add MSI interrupt feature support Zha Bin
2020-02-11  3:17   ` Jason Wang
2020-02-11  3:35     ` [virtio-dev] " Liu, Jing2
2020-02-11  4:02       ` Jason Wang
     [not found]         ` <5522f205-207b-b012-6631-3cc77dde3bfe@linux.intel.com>
2020-02-11  7:40           ` Jason Wang
2020-02-11 11:58             ` Michael S. Tsirkin
2020-02-11 12:04               ` Jason Wang
2020-02-11 12:08                 ` Michael S. Tsirkin
2020-02-11 12:18                   ` Jason Wang
2020-02-11 14:00                     ` Michael S. Tsirkin
2020-02-12  9:03                       ` Jason Wang
2020-02-12  9:15                         ` Michael S. Tsirkin
     [not found]             ` <4c19292f-9d25-a859-3dde-6dd5a03fdf0b@linux.intel.com>
2020-02-12  7:33               ` Michael S. Tsirkin
2020-02-12  9:06               ` Jason Wang
2020-02-12  9:16                 ` Michael S. Tsirkin
2020-02-13  3:40                   ` Jason Wang
2020-02-11 11:21       ` Michael S. Tsirkin
2020-02-11 11:11   ` Michael S. Tsirkin
2020-02-10  9:05 ` [PATCH v2 5/5] x86: virtio-mmio: support virtio-mmio with MSI for x86 Zha Bin
2020-02-11 11:14   ` Michael S. Tsirkin
2020-02-10 11:44 ` [PATCH v2 0/5] virtio mmio specification enhancement Michael S. Tsirkin
2020-02-11 16:05   ` Chao Peng
2020-02-11 10:57     ` Michael S. Tsirkin

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