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[79.176.41.183]) by smtp.gmail.com with ESMTPSA id r1sm1921438qtu.83.2020.02.11.02.50.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Feb 2020 02:50:52 -0800 (PST) Date: Tue, 11 Feb 2020 05:50:48 -0500 From: "Michael S. Tsirkin" To: Zha Bin 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 Message-ID: <20200211055005-mutt-send-email-mst@kernel.org> References: <8a4ea95d6d77a2814aaf6897b5517353289a098e.1581305609.git.zhabin@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8a4ea95d6d77a2814aaf6897b5517353289a098e.1581305609.git.zhabin@linux.alibaba.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 10, 2020 at 05:05:17PM +0800, Zha Bin wrote: > From: Liu Jiang > > 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 > Co-developed-by: Zha Bin > Signed-off-by: Zha Bin > Co-developed-by: Jing Liu > Signed-off-by: Jing Liu > Co-developed-by: Chao Peng > Signed-off-by: Chao Peng 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