Re: [PATCH] vdpa_sim_blk: add `capacity` module parameter

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

On Fri, Jul 05, 2024 at 01:28:21PM +0200, Stefano Garzarella wrote:
> The vDPA block simulator always allocated a 128 MiB ram-disk, but some
> filesystems (e.g. XFS) may require larger minimum sizes (see
> https://issues.redhat.com/browse/RHEL-45951).
> 
> So to allow us to test these filesystems, let's add a module parameter
> to control the size of the simulated virtio-blk devices.
> The value is mapped directly to the `capacity` field of the virtio-blk
> configuration space, so it must be expressed in sector numbers of 512
> bytes.
> 
> The default value (0x40000) is the same as the previous value, so the
> behavior without setting `capacity` remains unchanged.
> 
> Before this patch or with this patch without setting `capacity`:
>   $ modprobe vdpa-sim-blk
>   $ vdpa dev add mgmtdev vdpasim_blk name blk0
>   virtio_blk virtio6: 1/0/0 default/read/poll queues
>   virtio_blk virtio6: [vdb] 262144 512-byte logical blocks (134 MB/128 MiB)
> 
> After this patch:
>   $ modprobe vdpa-sim-blk capacity=614400
>   $ vdpa dev add mgmtdev vdpasim_blk name blk0
>   virtio_blk virtio6: 1/0/0 default/read/poll queues
>   virtio_blk virtio6: [vdb] 614400 512-byte logical blocks (315 MB/300 MiB)
> 
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

What a hack. Cindy was working on adding control over config
space, why can't that be used?

> ---
>  drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index b137f3679343..18f390149836 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -33,7 +33,6 @@
>  				 (1ULL << VIRTIO_BLK_F_DISCARD)  | \
>  				 (1ULL << VIRTIO_BLK_F_WRITE_ZEROES))
>  
> -#define VDPASIM_BLK_CAPACITY	0x40000
>  #define VDPASIM_BLK_SIZE_MAX	0x1000
>  #define VDPASIM_BLK_SEG_MAX	32
>  #define VDPASIM_BLK_DWZ_MAX_SECTORS UINT_MAX
> @@ -43,6 +42,10 @@
>  #define VDPASIM_BLK_AS_NUM	1
>  #define VDPASIM_BLK_GROUP_NUM	1
>  
> +static unsigned long capacity = 0x40000;
> +module_param(capacity, ulong, 0444);
> +MODULE_PARM_DESC(capacity, "virtio-blk device capacity (in 512-byte sectors)");
> +
>  struct vdpasim_blk {
>  	struct vdpasim vdpasim;
>  	void *buffer;
> @@ -79,10 +82,10 @@ static void vdpasim_blk_buffer_unlock(struct vdpasim_blk *blk)
>  static bool vdpasim_blk_check_range(struct vdpasim *vdpasim, u64 start_sector,
>  				    u64 num_sectors, u64 max_sectors)
>  {
> -	if (start_sector > VDPASIM_BLK_CAPACITY) {
> +	if (start_sector > capacity) {
>  		dev_dbg(&vdpasim->vdpa.dev,
> -			"starting sector exceeds the capacity - start: 0x%llx capacity: 0x%x\n",
> -			start_sector, VDPASIM_BLK_CAPACITY);
> +			"starting sector exceeds the capacity - start: 0x%llx capacity: 0x%lx\n",
> +			start_sector, capacity);
>  	}
>  
>  	if (num_sectors > max_sectors) {
> @@ -92,10 +95,10 @@ static bool vdpasim_blk_check_range(struct vdpasim *vdpasim, u64 start_sector,
>  		return false;
>  	}
>  
> -	if (num_sectors > VDPASIM_BLK_CAPACITY - start_sector) {
> +	if (num_sectors > capacity - start_sector) {
>  		dev_dbg(&vdpasim->vdpa.dev,
> -			"request exceeds the capacity - start: 0x%llx num: 0x%llx capacity: 0x%x\n",
> -			start_sector, num_sectors, VDPASIM_BLK_CAPACITY);
> +			"request exceeds the capacity - start: 0x%llx num: 0x%llx capacity: 0x%lx\n",
> +			start_sector, num_sectors, capacity);
>  		return false;
>  	}
>  
> @@ -369,7 +372,7 @@ static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
>  
>  	memset(config, 0, sizeof(struct virtio_blk_config));
>  
> -	blk_config->capacity = cpu_to_vdpasim64(vdpasim, VDPASIM_BLK_CAPACITY);
> +	blk_config->capacity = cpu_to_vdpasim64(vdpasim, capacity);
>  	blk_config->size_max = cpu_to_vdpasim32(vdpasim, VDPASIM_BLK_SIZE_MAX);
>  	blk_config->seg_max = cpu_to_vdpasim32(vdpasim, VDPASIM_BLK_SEG_MAX);
>  	blk_config->num_queues = cpu_to_vdpasim16(vdpasim, VDPASIM_BLK_VQ_NUM);
> @@ -437,8 +440,7 @@ static int vdpasim_blk_dev_add(struct vdpa_mgmt_dev *mdev, const char *name,
>  	if (blk->shared_backend) {
>  		blk->buffer = shared_buffer;
>  	} else {
> -		blk->buffer = kvzalloc(VDPASIM_BLK_CAPACITY << SECTOR_SHIFT,
> -				       GFP_KERNEL);
> +		blk->buffer = kvzalloc(capacity << SECTOR_SHIFT, GFP_KERNEL);
>  		if (!blk->buffer) {
>  			ret = -ENOMEM;
>  			goto put_dev;
> @@ -495,8 +497,7 @@ static int __init vdpasim_blk_init(void)
>  		goto parent_err;
>  
>  	if (shared_backend) {
> -		shared_buffer = kvzalloc(VDPASIM_BLK_CAPACITY << SECTOR_SHIFT,
> -					 GFP_KERNEL);
> +		shared_buffer = kvzalloc(capacity << SECTOR_SHIFT, GFP_KERNEL);
>  		if (!shared_buffer) {
>  			ret = -ENOMEM;
>  			goto mgmt_dev_err;
> -- 
> 2.45.2