From abebb16254b362664452e14d9711ddb54855ddcf Mon Sep 17 00:00:00 2001 From: Stefano Garzarella Date: Fri, 7 Apr 2023 15:36:58 +0200 Subject: [PATCH] vdpa_sim_blk: support shared backend The vdpa_sim_blk simulator uses a ramdisk as the backend. To test live migration, we need two devices that share the backend to have the data synchronized with each other. Add a new module parameter to make the buffer shared between all devices. The shared_buffer_mutex is used just to ensure that each operation is atomic, but it is up to the user to use the devices knowing that the underlying ramdisk is shared. For example, when we do a migration, the VMM (e.g., QEMU) will guarantee to write to the destination device, only after completing operations with the source device. Signed-off-by: Stefano Garzarella Message-Id: <20230407133658.66339-3-sgarzare@redhat.com> Signed-off-by: Michael S. Tsirkin --- drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 55 +++++++++++++++++++++++++--- 1 file changed, 49 insertions(+), 6 deletions(-) diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c index c996e750dc02..00d7d72713be 100644 --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c @@ -46,6 +46,7 @@ struct vdpasim_blk { struct vdpasim vdpasim; void *buffer; + bool shared_backend; }; static struct vdpasim_blk *sim_to_blk(struct vdpasim *vdpasim) @@ -55,6 +56,26 @@ static struct vdpasim_blk *sim_to_blk(struct vdpasim *vdpasim) static char vdpasim_blk_id[VIRTIO_BLK_ID_BYTES] = "vdpa_blk_sim"; +static bool shared_backend; +module_param(shared_backend, bool, 0444); +MODULE_PARM_DESC(shared_backend, "Enable the shared backend between virtio-blk devices"); + +static void *shared_buffer; +/* mutex to synchronize shared_buffer access */ +static DEFINE_MUTEX(shared_buffer_mutex); + +static void vdpasim_blk_buffer_lock(struct vdpasim_blk *blk) +{ + if (blk->shared_backend) + mutex_lock(&shared_buffer_mutex); +} + +static void vdpasim_blk_buffer_unlock(struct vdpasim_blk *blk) +{ + if (blk->shared_backend) + mutex_unlock(&shared_buffer_mutex); +} + static bool vdpasim_blk_check_range(struct vdpasim *vdpasim, u64 start_sector, u64 num_sectors, u64 max_sectors) { @@ -154,8 +175,10 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim, break; } + vdpasim_blk_buffer_lock(blk); bytes = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov, blk->buffer + offset, to_push); + vdpasim_blk_buffer_unlock(blk); if (bytes < 0) { dev_dbg(&vdpasim->vdpa.dev, "vringh_iov_push_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n", @@ -175,8 +198,10 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim, break; } + vdpasim_blk_buffer_lock(blk); bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->out_iov, blk->buffer + offset, to_pull); + vdpasim_blk_buffer_unlock(blk); if (bytes < 0) { dev_dbg(&vdpasim->vdpa.dev, "vringh_iov_pull_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n", @@ -256,8 +281,10 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim, } if (type == VIRTIO_BLK_T_WRITE_ZEROES) { + vdpasim_blk_buffer_lock(blk); memset(blk->buffer + offset, 0, num_sectors << SECTOR_SHIFT); + vdpasim_blk_buffer_unlock(blk); } break; @@ -366,7 +393,8 @@ static void vdpasim_blk_free(struct vdpasim *vdpasim) { struct vdpasim_blk *blk = sim_to_blk(vdpasim); - kvfree(blk->buffer); + if (!blk->shared_backend) + kvfree(blk->buffer); } static void vdpasim_blk_mgmtdev_release(struct device *dev) @@ -404,12 +432,17 @@ static int vdpasim_blk_dev_add(struct vdpa_mgmt_dev *mdev, const char *name, return PTR_ERR(simdev); blk = sim_to_blk(simdev); + blk->shared_backend = shared_backend; - blk->buffer = kvmalloc(VDPASIM_BLK_CAPACITY << SECTOR_SHIFT, - GFP_KERNEL); - if (!blk->buffer) { - ret = -ENOMEM; - goto put_dev; + if (blk->shared_backend) { + blk->buffer = shared_buffer; + } else { + blk->buffer = kvmalloc(VDPASIM_BLK_CAPACITY << SECTOR_SHIFT, + GFP_KERNEL); + if (!blk->buffer) { + ret = -ENOMEM; + goto put_dev; + } } ret = _vdpa_register_device(&simdev->vdpa, VDPASIM_BLK_VQ_NUM); @@ -461,6 +494,15 @@ static int __init vdpasim_blk_init(void) if (ret) goto parent_err; + if (shared_backend) { + shared_buffer = kvmalloc(VDPASIM_BLK_CAPACITY << SECTOR_SHIFT, + GFP_KERNEL); + if (!shared_buffer) { + ret = -ENOMEM; + goto parent_err; + } + } + return 0; parent_err: @@ -470,6 +512,7 @@ parent_err: static void __exit vdpasim_blk_exit(void) { + kvfree(shared_buffer); vdpa_mgmtdev_unregister(&mgmt_dev); device_unregister(&vdpasim_blk_mgmtdev); }