Commit e13a6915 authored by Stefano Garzarella's avatar Stefano Garzarella Committed by Michael S. Tsirkin
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vhost/vsock: add IOTLB API support 

This patch enables the IOTLB API support for vhost-vsock devices,
allowing the userspace to emulate an IOMMU for the guest.

These changes were made following vhost-net, in details this patch:
- exposes VIRTIO_F_ACCESS_PLATFORM feature and inits the iotlb
  device if the feature is acked
- implements VHOST_GET_BACKEND_FEATURES and
  VHOST_SET_BACKEND_FEATURES ioctls
- calls vq_meta_prefetch() before vq processing to prefetch vq
  metadata address in IOTLB
- provides .read_iter, .write_iter, and .poll callbacks for the
  chardev; they are used by the userspace to exchange IOTLB messages

This patch was tested specifying "intel_iommu=strict" in the guest
kernel command line. I used QEMU with a patch applied [1] to fix a
simple issue (that patch was merged in QEMU v5.2.0):
    $ qemu -M q35,accel=kvm,kernel-irqchip=split \
           -drive file=fedora.qcow2,format=qcow2,if=virtio \
           -device intel-iommu,intremap=on,device-iotlb=on \
           -device vhost-vsock-pci,guest-cid=3,iommu_platform=on,ats=on

[1] https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg09077.html



Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarStefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20201223143638.123417-1-sgarzare@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
parent 418eddef

drivers/vhost/vsock.c

+65 −3
Original line number Diff line number Diff line
@@ -30,7 +30,12 @@ 
#define VHOST_VSOCK_PKT_WEIGHT 256



enum {

	VHOST_VSOCK_FEATURES = VHOST_FEATURES,

	VHOST_VSOCK_FEATURES = VHOST_FEATURES |

			       (1ULL << VIRTIO_F_ACCESS_PLATFORM)

};



enum {

	VHOST_VSOCK_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)

};



/* Used to track all the vhost_vsock instances on the system. */
@@ -94,6 +99,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock, 
	if (!vhost_vq_get_backend(vq))

		goto out;



	if (!vq_meta_prefetch(vq))

		goto out;



	/* Avoid further vmexits, we're already processing the virtqueue */

	vhost_disable_notify(&vsock->dev, vq);
@@ -449,6 +457,9 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work) 
	if (!vhost_vq_get_backend(vq))

		goto out;



	if (!vq_meta_prefetch(vq))

		goto out;



	vhost_disable_notify(&vsock->dev, vq);

	do {

		u32 len;
@@ -766,8 +777,12 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features) 
	mutex_lock(&vsock->dev.mutex);

	if ((features & (1 << VHOST_F_LOG_ALL)) &&

	    !vhost_log_access_ok(&vsock->dev)) {

		mutex_unlock(&vsock->dev.mutex);

		return -EFAULT;

		goto err;

	}



	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {

		if (vhost_init_device_iotlb(&vsock->dev, true))

			goto err;

	}



	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
@@ -778,6 +793,10 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features) 
	}

	mutex_unlock(&vsock->dev.mutex);

	return 0;



err:

	mutex_unlock(&vsock->dev.mutex);

	return -EFAULT;

}



static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
@@ -811,6 +830,18 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl, 
		if (copy_from_user(&features, argp, sizeof(features)))

			return -EFAULT;

		return vhost_vsock_set_features(vsock, features);

	case VHOST_GET_BACKEND_FEATURES:

		features = VHOST_VSOCK_BACKEND_FEATURES;

		if (copy_to_user(argp, &features, sizeof(features)))

			return -EFAULT;

		return 0;

	case VHOST_SET_BACKEND_FEATURES:

		if (copy_from_user(&features, argp, sizeof(features)))

			return -EFAULT;

		if (features & ~VHOST_VSOCK_BACKEND_FEATURES)

			return -EOPNOTSUPP;

		vhost_set_backend_features(&vsock->dev, features);

		return 0;

	default:

		mutex_lock(&vsock->dev.mutex);

		r = vhost_dev_ioctl(&vsock->dev, ioctl, argp);
@@ -823,6 +854,34 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl, 
	}

}



static ssize_t vhost_vsock_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)

{

	struct file *file = iocb->ki_filp;

	struct vhost_vsock *vsock = file->private_data;

	struct vhost_dev *dev = &vsock->dev;

	int noblock = file->f_flags & O_NONBLOCK;



	return vhost_chr_read_iter(dev, to, noblock);

}



static ssize_t vhost_vsock_chr_write_iter(struct kiocb *iocb,

					struct iov_iter *from)

{

	struct file *file = iocb->ki_filp;

	struct vhost_vsock *vsock = file->private_data;

	struct vhost_dev *dev = &vsock->dev;



	return vhost_chr_write_iter(dev, from);

}



static __poll_t vhost_vsock_chr_poll(struct file *file, poll_table *wait)

{

	struct vhost_vsock *vsock = file->private_data;

	struct vhost_dev *dev = &vsock->dev;



	return vhost_chr_poll(file, dev, wait);

}



static const struct file_operations vhost_vsock_fops = {

	.owner          = THIS_MODULE,

	.open           = vhost_vsock_dev_open,
@@ -830,6 +889,9 @@ static const struct file_operations vhost_vsock_fops = { 
	.llseek		= noop_llseek,

	.unlocked_ioctl = vhost_vsock_dev_ioctl,

	.compat_ioctl   = compat_ptr_ioctl,

	.read_iter      = vhost_vsock_chr_read_iter,

	.write_iter     = vhost_vsock_chr_write_iter,

	.poll           = vhost_vsock_chr_poll,

};



static struct miscdevice vhost_vsock_misc = {