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From: Zha Bin <zhabin@linux.alibaba.com>
To: linux-kernel@vger.kernel.org
Cc: mst@redhat.com, jasowang@redhat.com, slp@redhat.com,
	virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org,
	gerry@linux.alibaba.com, zhabin@linux.alibaba.com,
	jing2.liu@linux.intel.com, chao.p.peng@linux.intel.com
Subject: [PATCH v2 1/5] virtio-mmio: add notify feature for per-queue
Date: Mon, 10 Feb 2020 17:05:17 +0800	[thread overview]
Message-ID: <8a4ea95d6d77a2814aaf6897b5517353289a098e.1581305609.git.zhabin@linux.alibaba.com> (raw)
In-Reply-To: <cover.1581305609.git.zhabin@linux.alibaba.com>
In-Reply-To: <cover.1581305609.git.zhabin@linux.alibaba.com>

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>
---
 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:[~2020-02-10  9:05 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 ` Zha Bin [this message]
2020-02-11 10:50   ` [PATCH v2 1/5] virtio-mmio: add notify feature for per-queue Michael S. Tsirkin
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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