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Subject[PATCH v3 12/13] vdpa_sim_blk: implement ramdisk behaviour
Date
The previous implementation wrote only the status of each request.
This patch implements a more accurate block device simulator,
providing a ramdisk-like behavior and adding input validation.

Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
v2:
- used %zd %zx to print size_t and ssize_t variables in dev_err()
- removed unnecessary new line [Jason]
- moved VIRTIO_BLK_T_GET_ID in another patch [Jason]
- used push/pull instead of write/read terminology
- added vdpasim_blk_check_range() to avoid overflows [Stefan]
- use vdpasim*_to_cpu instead of le*_to_cpu
- used vringh_kiov_length() helper [Jason]
---
drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 164 ++++++++++++++++++++++++---
1 file changed, 146 insertions(+), 18 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
index 9822f9edc511..2652a499fb34 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -3,6 +3,7 @@
* VDPA simulator for block device.
*
* Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
+ * Copyright (c) 2021, Red Hat Inc. All rights reserved.
*
*/

@@ -13,6 +14,7 @@
#include <linux/sched.h>
#include <linux/vringh.h>
#include <linux/vdpa.h>
+#include <linux/blkdev.h>
#include <uapi/linux/virtio_blk.h>

#include "vdpa_sim.h"
@@ -36,10 +38,151 @@

static struct vdpasim *vdpasim_blk_dev;

+static bool vdpasim_blk_check_range(u64 start_sector, size_t range_size)
+{
+ u64 range_sectors = range_size >> SECTOR_SHIFT;
+
+ if (range_size > VDPASIM_BLK_SIZE_MAX * VDPASIM_BLK_SEG_MAX)
+ return false;
+
+ if (start_sector > VDPASIM_BLK_CAPACITY)
+ return false;
+
+ if (range_sectors > VDPASIM_BLK_CAPACITY - start_sector)
+ return false;
+
+ return true;
+}
+
+/* Returns 'true' if the request is handled (with or without an I/O error)
+ * and the status is correctly written in the last byte of the 'in iov',
+ * 'false' otherwise.
+ */
+static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
+ struct vdpasim_virtqueue *vq)
+{
+ size_t pushed = 0, to_pull, to_push;
+ struct virtio_blk_outhdr hdr;
+ ssize_t bytes;
+ loff_t offset;
+ u64 sector;
+ u8 status;
+ u32 type;
+ int ret;
+
+ ret = vringh_getdesc_iotlb(&vq->vring, &vq->out_iov, &vq->in_iov,
+ &vq->head, GFP_ATOMIC);
+ if (ret != 1)
+ return false;
+
+ if (vq->out_iov.used < 1 || vq->in_iov.used < 1) {
+ dev_err(&vdpasim->vdpa.dev, "missing headers - out_iov: %u in_iov %u\n",
+ vq->out_iov.used, vq->in_iov.used);
+ return false;
+ }
+
+ if (vq->in_iov.iov[vq->in_iov.used - 1].iov_len < 1) {
+ dev_err(&vdpasim->vdpa.dev, "request in header too short\n");
+ return false;
+ }
+
+ /* The last byte is the status and we checked if the last iov has
+ * enough room for it.
+ */
+ to_push = vringh_kiov_length(&vq->in_iov) - 1;
+
+ to_pull = vringh_kiov_length(&vq->out_iov);
+
+ bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->out_iov, &hdr,
+ sizeof(hdr));
+ if (bytes != sizeof(hdr)) {
+ dev_err(&vdpasim->vdpa.dev, "request out header too short\n");
+ return false;
+ }
+
+ to_pull -= bytes;
+
+ type = vdpasim32_to_cpu(vdpasim, hdr.type);
+ sector = vdpasim64_to_cpu(vdpasim, hdr.sector);
+ offset = sector << SECTOR_SHIFT;
+ status = VIRTIO_BLK_S_OK;
+
+ switch (type) {
+ case VIRTIO_BLK_T_IN:
+ if (!vdpasim_blk_check_range(sector, to_push)) {
+ dev_err(&vdpasim->vdpa.dev,
+ "reading over the capacity - offset: 0x%llx len: 0x%zx\n",
+ offset, to_push);
+ status = VIRTIO_BLK_S_IOERR;
+ break;
+ }
+
+ bytes = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov,
+ vdpasim->buffer + offset,
+ to_push);
+ if (bytes < 0) {
+ dev_err(&vdpasim->vdpa.dev,
+ "vringh_iov_push_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n",
+ bytes, offset, to_push);
+ status = VIRTIO_BLK_S_IOERR;
+ break;
+ }
+
+ pushed += bytes;
+ break;
+
+ case VIRTIO_BLK_T_OUT:
+ if (!vdpasim_blk_check_range(sector, to_pull)) {
+ dev_err(&vdpasim->vdpa.dev,
+ "writing over the capacity - offset: 0x%llx len: 0x%zx\n",
+ offset, to_pull);
+ status = VIRTIO_BLK_S_IOERR;
+ break;
+ }
+
+ bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->out_iov,
+ vdpasim->buffer + offset,
+ to_pull);
+ if (bytes < 0) {
+ dev_err(&vdpasim->vdpa.dev,
+ "vringh_iov_pull_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n",
+ bytes, offset, to_pull);
+ status = VIRTIO_BLK_S_IOERR;
+ break;
+ }
+ break;
+
+ default:
+ dev_warn(&vdpasim->vdpa.dev,
+ "Unsupported request type %d\n", type);
+ status = VIRTIO_BLK_S_IOERR;
+ break;
+ }
+
+ /* If some operations fail, we need to skip the remaining bytes
+ * to put the status in the last byte
+ */
+ if (to_push - pushed > 0)
+ vringh_kiov_advance(&vq->in_iov, to_push - pushed);
+
+ /* Last byte is the status */
+ bytes = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov, &status, 1);
+ if (bytes != 1)
+ return false;
+
+ pushed += bytes;
+
+ /* Make sure data is wrote before advancing index */
+ smp_wmb();
+
+ vringh_complete_iotlb(&vq->vring, vq->head, pushed);
+
+ return true;
+}
+
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);
@@ -53,22 +196,7 @@ static void vdpasim_blk_work(struct work_struct *work)
if (!vq->ready)
continue;

- while (vringh_getdesc_iotlb(&vq->vring, &vq->out_iov,
- &vq->in_iov, &vq->head,
- GFP_ATOMIC) > 0) {
- int write;
-
- vq->in_iov.i = vq->in_iov.used - 1;
- write = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov,
- &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)) {
/* Make sure used is visible before rasing the interrupt. */
smp_wmb();

@@ -109,7 +237,7 @@ static int __init vdpasim_blk_init(void)
dev_attr.config_size = sizeof(struct virtio_blk_config);
dev_attr.get_config = vdpasim_blk_get_config;
dev_attr.work_fn = vdpasim_blk_work;
- dev_attr.buffer_size = PAGE_SIZE;
+ dev_attr.buffer_size = VDPASIM_BLK_CAPACITY << SECTOR_SHIFT;

vdpasim_blk_dev = vdpasim_create(&dev_attr);
if (IS_ERR(vdpasim_blk_dev)) {
--
2.29.2
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