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Date: Mon, 16 Nov 2020 04:50:43 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: virtualization@...ts.linux-foundation.org,
Stefan Hajnoczi <stefanha@...hat.com>,
Laurent Vivier <lvivier@...hat.com>,
linux-kernel@...r.kernel.org, Eli Cohen <elic@...dia.com>,
Jason Wang <jasowang@...hat.com>,
Max Gurtovoy <mgurtovoy@...dia.com>
Subject: Re: [PATCH RFC 12/12] vdpa_sim_blk: implement ramdisk behaviour
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@...hat.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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