Re: [PATCH RFC 12/12] vdpa_sim_blk: implement ramdisk behaviour

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Nov 13, 2020 at 02:47:12PM +0100, Stefano Garzarella wrote:
> The previous implementation wrote only the status of each request.
> This patch implements a more accurate block device simulator,
> providing a ramdisk-like behavior.
> 
> Also handle VIRTIO_BLK_T_GET_ID request, always answering the
> "vdpa_blk_sim" string.

Maybe an ioctl to specify the id makes more sense.

> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>  drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 151 +++++++++++++++++++++++----
>  1 file changed, 133 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index 8e41b3ab98d5..68e74383322f 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -7,6 +7,7 @@
>   */
>  
>  #include <linux/module.h>
> +#include <linux/blkdev.h>
>  #include <uapi/linux/virtio_blk.h>
>  
>  #include "vdpa_sim.h"
> @@ -24,10 +25,137 @@
>  
>  static struct vdpasim *vdpasim_blk_dev;
>  
> +static int vdpasim_blk_handle_req(struct vdpasim *vdpasim,
> +				  struct vdpasim_virtqueue *vq)
> +{
> +	size_t wrote = 0, to_read = 0, to_write = 0;
> +	struct virtio_blk_outhdr hdr;
> +	uint8_t status;
> +	uint32_t type;
> +	ssize_t bytes;
> +	loff_t offset;
> +	int i, ret;
> +
> +	vringh_kiov_cleanup(&vq->riov);
> +	vringh_kiov_cleanup(&vq->wiov);
> +
> +	ret = vringh_getdesc_iotlb(&vq->vring, &vq->riov, &vq->wiov,
> +				   &vq->head, GFP_ATOMIC);
> +	if (ret != 1)
> +		return ret;
> +
> +	for (i = 0; i < vq->wiov.used; i++)
> +		to_write += vq->wiov.iov[i].iov_len;
> +	to_write -= 1; /* last byte is the status */
> +
> +	for (i = 0; i < vq->riov.used; i++)
> +		to_read += vq->riov.iov[i].iov_len;
> +
> +	bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->riov, &hdr, sizeof(hdr));
> +	if (bytes != sizeof(hdr))
> +		return 0;
> +
> +	to_read -= bytes;
> +
> +	type = le32_to_cpu(hdr.type);
> +	offset = le64_to_cpu(hdr.sector) << SECTOR_SHIFT;
> +	status = VIRTIO_BLK_S_OK;
> +
> +	switch (type) {
> +	case VIRTIO_BLK_T_IN:
> +		if (offset + to_write > VDPASIM_BLK_CAPACITY << SECTOR_SHIFT) {
> +			dev_err(&vdpasim->vdpa.dev,
> +				"reading over the capacity - offset: 0x%llx len: 0x%lx\n",
> +				offset, to_write);
> +			status = VIRTIO_BLK_S_IOERR;
> +			break;
> +		}
> +
> +		bytes = vringh_iov_push_iotlb(&vq->vring, &vq->wiov,
> +					      vdpasim->buffer + offset,
> +					      to_write);
> +		if (bytes < 0) {
> +			dev_err(&vdpasim->vdpa.dev,
> +				"vringh_iov_push_iotlb() error: %ld offset: 0x%llx len: 0x%lx\n",
> +				bytes, offset, to_write);
> +			status = VIRTIO_BLK_S_IOERR;
> +			break;
> +		}
> +
> +		wrote += bytes;
> +		break;
> +
> +	case VIRTIO_BLK_T_OUT:
> +		if (offset + to_read > VDPASIM_BLK_CAPACITY << SECTOR_SHIFT) {
> +			dev_err(&vdpasim->vdpa.dev,
> +				"writing over the capacity - offset: 0x%llx len: 0x%lx\n",
> +				offset, to_read);
> +			status = VIRTIO_BLK_S_IOERR;
> +			break;
> +		}
> +
> +		bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->riov,
> +					      vdpasim->buffer + offset,
> +					      to_read);
> +		if (bytes < 0) {
> +			dev_err(&vdpasim->vdpa.dev,
> +				"vringh_iov_pull_iotlb() error: %ld offset: 0x%llx len: 0x%lx\n",
> +				bytes, offset, to_read);
> +			status = VIRTIO_BLK_S_IOERR;
> +			break;
> +		}
> +		break;
> +
> +	case VIRTIO_BLK_T_GET_ID: {
> +		char id[VIRTIO_BLK_ID_BYTES] = "vdpa_blk_sim";
> +
> +		bytes = vringh_iov_push_iotlb(&vq->vring,
> +					      &vq->wiov, id,
> +					      VIRTIO_BLK_ID_BYTES);
> +		if (bytes < 0) {
> +			dev_err(&vdpasim->vdpa.dev,
> +				"vringh_iov_push_iotlb() error: %ld\n", bytes);
> +			status = VIRTIO_BLK_S_IOERR;
> +			break;
> +		}
> +
> +		wrote += bytes;
> +		break;
> +	}
> +
> +	default:
> +		dev_warn(&vdpasim->vdpa.dev,
> +			 "Unsupported request type %d\n", type);
> +		status = VIRTIO_BLK_S_IOERR;
> +		break;
> +	}
> +
> +	/* if VIRTIO_BLK_T_IN or VIRTIO_BLK_T_GET_ID fail, we need to skip
> +	 * the remaining bytes to put the status in the last byte
> +	 */
> +	if (to_write - wrote > 0) {
> +		vringh_iov_push_iotlb(&vq->vring, &vq->wiov, NULL,
> +				      to_write - wrote);
> +	}
> +
> +	/* last byte is the status */
> +	bytes = vringh_iov_push_iotlb(&vq->vring, &vq->wiov, &status, 1);
> +	if (bytes != 1)
> +		return 0;
> +
> +	wrote += bytes;
> +
> +	/* Make sure data is wrote before advancing index */
> +	smp_wmb();
> +
> +	vringh_complete_iotlb(&vq->vring, vq->head, wrote);
> +
> +	return ret;
> +}
> +
>  static void vdpasim_blk_work(struct work_struct *work)
>  {
>  	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
> -	u8 status = VIRTIO_BLK_S_OK;
>  	int i;
>  
>  	spin_lock(&vdpasim->lock);
> @@ -41,21 +169,7 @@ static void vdpasim_blk_work(struct work_struct *work)
>  		if (!vq->ready)
>  			continue;
>  
> -		while (vringh_getdesc_iotlb(&vq->vring, &vq->riov, &vq->wiov,
> -					    &vq->head, GFP_ATOMIC) > 0) {
> -
> -			int write;
> -
> -			vq->wiov.i = vq->wiov.used - 1;
> -			write = vringh_iov_push_iotlb(&vq->vring, &vq->wiov, &status, 1);
> -			if (write <= 0)
> -				break;
> -
> -			/* Make sure data is wrote before advancing index */
> -			smp_wmb();
> -
> -			vringh_complete_iotlb(&vq->vring, vq->head, write);
> -
> +		while (vdpasim_blk_handle_req(vdpasim, vq) > 0) {
>  			/* Make sure used is visible before rasing the interrupt. */
>  			smp_wmb();
>  
> @@ -67,6 +181,7 @@ static void vdpasim_blk_work(struct work_struct *work)
>  				vq->cb(vq->private);
>  			local_bh_enable();
>  		}
> +
>  	}
>  out:
>  	spin_unlock(&vdpasim->lock);
> @@ -84,7 +199,7 @@ static void vdpasim_blk_update_config(struct vdpasim *vdpasim)
>  	config->num_queues = cpu_to_vdpasim16(vdpasim, VDPASIM_BLK_VQ_NUM);
>  	config->min_io_size = cpu_to_vdpasim16(vdpasim, 1);
>  	config->opt_io_size = cpu_to_vdpasim32(vdpasim, 1);
> -	config->blk_size = cpu_to_vdpasim32(vdpasim, 512);
> +	config->blk_size = cpu_to_vdpasim32(vdpasim, SECTOR_SIZE);
>  }
>  
>  static int __init vdpasim_blk_init(void)
> @@ -100,7 +215,7 @@ static int __init vdpasim_blk_init(void)
>  	attr.device.update_config = vdpasim_blk_update_config;
>  
>  	attr.work_fn = vdpasim_blk_work;
> -	attr.buffer_size = PAGE_SIZE;
> +	attr.buffer_size = VDPASIM_BLK_CAPACITY << SECTOR_SHIFT;
>  
>  	vdpasim_blk_dev = vdpasim_create(&attr);
>  	if (IS_ERR(vdpasim_blk_dev)) {
> -- 
> 2.26.2

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