From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 4/6] KVM: Add kvm_get_irq_routing_entry() func Date: Thu, 18 Nov 2010 11:41:51 +0200 Message-ID: <20101118094151.GJ16832@redhat.com> References: <1289812532-3227-1-git-send-email-sheng@linux.intel.com> <1289812532-3227-5-git-send-email-sheng@linux.intel.com> <4CE3E045.30500@redhat.com> <201011181022.15853.sheng@linux.intel.com> <4CE4F247.9080203@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sheng Yang , Marcelo Tosatti , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:63446 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755992Ab0KRJmC (ORCPT ); Thu, 18 Nov 2010 04:42:02 -0500 Content-Disposition: inline In-Reply-To: <4CE4F247.9080203@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Nov 18, 2010 at 11:30:47AM +0200, Avi Kivity wrote: > >> > >> *entry may be stale after rcu_read_unlock(). Is this a problem? > > > >I suppose not. All MSI-X MMIO accessing would be executed without delay, so no re- > >order issue would happen. If the guest is reading and writing the field at the same > >time(from two cpus), it should got some kinds of sync method for itself - or it > >may not care what's the reading result(like the one after msix_mask_irq()). > > I guess so. Michael/Alex? This is kvm_get_irq_routing_entry which is used for table reads, correct? Actually, the pci read *is* the sync method that guests use, they rely on reads to flush out all previous writes. > -- > error compiling committee.c: too many arguments to function