> -----Original Message----- > From: Radim Krcmár [mailto:rkrc...@redhat.com] > Sent: Monday, January 25, 2016 10:06 PM > To: Wu, Feng <feng...@intel.com> > Cc: Paolo Bonzini <pbonz...@redhat.com>; linux-kernel@vger.kernel.org; > k...@vger.kernel.org > Subject: Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the > interrupt is not single-destination > > 2016-01-25 12:26+0000, Wu, Feng: > >> From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo > >> It may be necessary because IRTE writes (128 bits) are not atomic. > > > > IRTE is updated atomically, I added the patch to support this. Please > > refer to 344cb4e0b6f3a0dbef0643eacb4946338eb228c0. > > I also think that SN bit is not affected by atomicity: if the IRTE could > have been read half-updated while changing from posted to non-posted, > then it wouldn't point to the correct PID, because its address is not > within 64 bits, so the SN bit wouldn't matter.
Yes, like the comments in the commit, we should atomically update the IRTE in PI case (PI -> non-PI, non-PI -> PI), without which, it cannot guarantee the correctness, since 'pda' is not within 64 bits, like Radim pointed out above. Thanks, Feng > > IRTE invalidation seems important in VT-d ...
