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

Stefano Garzarella
2020-11-13T13:49:25Z

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.

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