On Thu, Aug 03, 2017 at 02:31:02AM -0700, Bin Meng wrote:
Maximum Data Transfer Size (MDTS) field indicates the maximum data transfer size between the host and the controller. The host should not submit a command that exceeds this transfer size. The value is in units of the minimum memory page size and is reported as a power of two (2^n).
The spec also says: a value of 0h indicates no restrictions on transfer size. On the real NVMe card this is normally not 0 due to hardware restrictions, but with QEMU emulated NVMe device it reports as 0. In nvme_blk_read/write() below we have the following algorithm for maximum number of logic blocks per transfer:
u16 lbas = 1 << (dev->max_transfer_shift - ns->lba_shift);
dev->max_transfer_shift being 0 will for sure cause lbas to overflow. Let's use 20. With this fix, the NVMe driver works on QEMU emulated NVMe device.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
Reviewed-by: Tom Rini trini@konsulko.com