Re: [Qemu-block] [SPDK] How to setup a QEMU system disk by using SPDK?

[Harris, James R]

On 6/4/18, 5:52 AM, "SPDK on behalf of Stefan Hajnoczi" <address@hidden on 
behalf of address@hidden> wrote:

    On Mon, Jun 04, 2018 at 03:46:16PM +0800, Bob Chen wrote:
    > Hi, guys
    > 
    > I have setup a SPDK lvol as a data disk, and run QEMU with it, as per the
    > vhost documents instructed.
    > 
    > Then I exposed a empty lvol to host nbd, and used `dd` to copy a existing
    > raw disk into lvol, which contains a guest OS. But the guest was not able
    > to boot.
    > 
    > Was there any step that I missed?
    
    Please post your QEMU command-line, spdk command-line, and the error
  message that you got.

I suspect this is because all SPDK logical volumes are exposed with 4KB logical 
block size.  IIRC, Seabios legacy boot doesn’t support 4KB logical block 
devices.  UEFI boot should work but we don’t have automated tests set up for 
that yet.

I think SPDK logical volumes could be exposed with 512 byte logical block size, 
if the underlying block device has a 512 byte logical block size.  Using 4KB 
LBA simplified the implementation a bit and all metadata has to use 4KB for 
atomicity.  But talking with Ben we don’t see any reason 512 byte for 
read/write/unmap operations wouldn’t work.  We may have to use feature bits 
though so that this change in behavior only applies to newly created logical 
volumes. 

Bob – I’m curious if you can boot your VM with the SPDK logical volume as a 
secondary disk?

-Jim