Re: [Qemu-devel] [PATCH] NVMe: Initial commit to add an NVM Express device

[Stefan Hajnoczi]

On Mon, Dec 10, 2012 at 1:36 PM, Kevin Wolf <address@hidden> wrote:
> Hi Keith,
>
> Am 08.12.2012 20:20, schrieb Keith Busch:
>>> IIUC from the website above, NVMe is to be used with SSDs?  It would be
>>> good to add to the commit message how to actually use the device
>>> command-line-wise beyond the obvious -device nvme: I did not spot on
>>> brief sight where you expose a bus to add drives (nor a special IF_*
>>> interface type to assign to a drive), so others might wonder as well.
>>
>> Actually the nvme device _is_ the SSD. The emulated controller here
>> creates files to use for its backing storage so you don't add
>> additional drives, if that makes sense.
>
> I think the device would be much more useful if you could make it use
> the qemu block layer instead of implementing your own functions for only
> raw images and only with a given magic file name.

Quick pointers to get started on Kevin's suggestion:

bdrv_aio_readv(), bdrv_aio_writev(), bdrv_aio_flush(), and
bdrv_aio_discard() provide the block device operations that emulated
storage controllers use.

Take a look at hw/virtio-blk.c to see how to take a -device
nvme,drive=<drive> (internally this is your BlockDriverState*).

Stefan