On Wed, Jul 17, 2013 at 9:27 AM, Paolo Bonzini <pbonz...@redhat.com> wrote: > Il 17/07/2013 17:54, ronnie sahlberg ha scritto: >> I think it is reasonable to assume that IF LBPRZ==1 and IF it is an >> "optimal unmap request" then the blocks will become unmapped and they >> will read back as 0. > > Yes, but it is not reasonable to assume that bdrv_discard will only > receive "optimal" requests. Thus, using WRITE SAME for LBPRZ=1, and not > exposing LBPRZ=1 if LBPWS=0 (may also use LBPWS10 depending on the > capacity), is the safer thing to do. > > Paolo
ACK. WRITESAME10/16 with UNMAP flag set is probably best.
