On Tue, Apr 2, 2013 at 10:27 PM, Keith Busch <keith.bu...@intel.com> wrote: > On Fri, 19 Apr 2013, Stefan Hajnoczi wrote: >> >> I don't see bdrv_aio_flush() in this patch. How does the guest ensure >> that data is safely on persistent storage (e.g. protected against data >> loss by power failure). > > > Great point! This is to be consistent with the NVMe spec. This commit > is the bare minimum, and an NVMe flush command is supported only if the > device reports having a Volatile Write Cache and it being enabled. Both > of these things are optional so they are ommitted in this commit. My > branch of QEMU supports the entirety of the specification including > flush and I hope to make it publicly available, but that was just too > big a commit to send for consideration.
Okay, great. I think I've even seen the additional code in your previous version. The lack of flush means this device should only be used with -drive cache=writethrough or cache=directsync so that QEMU uses fdatasync(2) to flush after writes. Stefan
