From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753031AbbFSQdv (ORCPT ); Fri, 19 Jun 2015 12:33:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33877 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752072AbbFSQdm (ORCPT ); Fri, 19 Jun 2015 12:33:42 -0400 Date: Fri, 19 Jun 2015 18:33:39 +0200 From: "Michael S. Tsirkin" To: Paolo Bonzini Cc: Igor Mammedov , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, andrey@xdel.ru Subject: Re: [PATCH 3/5] vhost: support upto 509 memory regions Message-ID: <20150619183226-mutt-send-email-mst@redhat.com> References: <20150619095515-mutt-send-email-mst@redhat.com> <5583CB62.6030405@redhat.com> <20150619100409-mutt-send-email-mst@redhat.com> <5583D85F.7090200@redhat.com> <20150619120734-mutt-send-email-mst@redhat.com> <5583F28A.9080206@redhat.com> <20150619153248-mutt-send-email-mst@redhat.com> <55843310.50403@redhat.com> <20150619181845-mutt-send-email-mst@redhat.com> <558442B3.2020900@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <558442B3.2020900@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 19, 2015 at 06:26:27PM +0200, Paolo Bonzini wrote: > > > On 19/06/2015 18:20, Michael S. Tsirkin wrote: > > > We could, but I/O is just an example. It can be I/O, a network ring, > > > whatever. We cannot audit all address_space_map uses. > > > > > > > No need to audit them all: defer device_add using an hva range until > > address_space_unmap drops using hvas in range drops reference count to > > 0. > > That could be forever. You certainly don't want to lockup the monitor > forever just because a device model isn't too friendly to memory hot-unplug. We can defer the addition, no need to lockup the monitor. > That's why you need to audit them (also, it's perfectly in the device > model's right to use address_space_unmap this way: it's the guest that's > buggy and leaves a dangling reference to a region before unplugging it). > > Paolo Then maybe it's not too bad that the guest will crash because the memory was unmapped. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/ From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 3/5] vhost: support upto 509 memory regions Date: Fri, 19 Jun 2015 18:33:39 +0200 Message-ID: <20150619183226-mutt-send-email-mst@redhat.com> References: <20150619095515-mutt-send-email-mst@redhat.com> <5583CB62.6030405@redhat.com> <20150619100409-mutt-send-email-mst@redhat.com> <5583D85F.7090200@redhat.com> <20150619120734-mutt-send-email-mst@redhat.com> <5583F28A.9080206@redhat.com> <20150619153248-mutt-send-email-mst@redhat.com> <55843310.50403@redhat.com> <20150619181845-mutt-send-email-mst@redhat.com> <558442B3.2020900@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Igor Mammedov , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, andrey@xdel.ru To: Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33877 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752072AbbFSQdm (ORCPT ); Fri, 19 Jun 2015 12:33:42 -0400 Content-Disposition: inline In-Reply-To: <558442B3.2020900@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Jun 19, 2015 at 06:26:27PM +0200, Paolo Bonzini wrote: > > > On 19/06/2015 18:20, Michael S. Tsirkin wrote: > > > We could, but I/O is just an example. It can be I/O, a network ring, > > > whatever. We cannot audit all address_space_map uses. > > > > > > > No need to audit them all: defer device_add using an hva range until > > address_space_unmap drops using hvas in range drops reference count to > > 0. > > That could be forever. You certainly don't want to lockup the monitor > forever just because a device model isn't too friendly to memory hot-unplug. We can defer the addition, no need to lockup the monitor. > That's why you need to audit them (also, it's perfectly in the device > model's right to use address_space_unmap this way: it's the guest that's > buggy and leaves a dangling reference to a region before unplugging it). > > Paolo Then maybe it's not too bad that the guest will crash because the memory was unmapped. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in