From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [RFC PATCH 0/3] Balloon inhibit enhancements Date: Mon, 30 Jul 2018 17:51:28 +0300 Message-ID: <20180730174601-mutt-send-email-mst@kernel.org> References: <20180717222721.14019.27548.stgit@gimli.home> <20180730163123-mutt-send-email-mst@kernel.org> <20180730083939.23f3b9cc@t450s.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org To: Alex Williamson Return-path: Content-Disposition: inline In-Reply-To: <20180730083939.23f3b9cc@t450s.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On Mon, Jul 30, 2018 at 08:39:39AM -0600, Alex Williamson wrote: > This is more > compatible with the IOMMU mappings, Precisely. These are at page granularity. > but I don't think it can be done > atomically with respect to inflight DMA of a physical device where we > cannot halt the device without interfering with its state. Guests never add pages to the balloon if they are under DMA, so that's fine - there's never an in-flight DMA, if there is guest is buggy and it's ok to crash it. -- MST From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39565) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fk9WJ-0004Xj-FH for qemu-devel@nongnu.org; Mon, 30 Jul 2018 10:51:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fk9WG-0001B3-Uy for qemu-devel@nongnu.org; Mon, 30 Jul 2018 10:51:35 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36766 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fk9WG-0001Aj-Px for qemu-devel@nongnu.org; Mon, 30 Jul 2018 10:51:32 -0400 Date: Mon, 30 Jul 2018 17:51:28 +0300 From: "Michael S. Tsirkin" Message-ID: <20180730174601-mutt-send-email-mst@kernel.org> References: <20180717222721.14019.27548.stgit@gimli.home> <20180730163123-mutt-send-email-mst@kernel.org> <20180730083939.23f3b9cc@t450s.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180730083939.23f3b9cc@t450s.home> Subject: Re: [Qemu-devel] [RFC PATCH 0/3] Balloon inhibit enhancements List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org On Mon, Jul 30, 2018 at 08:39:39AM -0600, Alex Williamson wrote: > This is more > compatible with the IOMMU mappings, Precisely. These are at page granularity. > but I don't think it can be done > atomically with respect to inflight DMA of a physical device where we > cannot halt the device without interfering with its state. Guests never add pages to the balloon if they are under DMA, so that's fine - there's never an in-flight DMA, if there is guest is buggy and it's ok to crash it. -- MST