From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34120) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fE8uE-0006KU-As for qemu-devel@nongnu.org; Thu, 03 May 2018 03:43:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fE8uB-0001GD-Nl for qemu-devel@nongnu.org; Thu, 03 May 2018 03:43:58 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:60208 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 1fE8uB-0001Fx-Iu for qemu-devel@nongnu.org; Thu, 03 May 2018 03:43:55 -0400 References: <20180425045129.17449-9-peterx@redhat.com> <2b05e076-0af9-0ee9-c076-7acc29714913@redhat.com> <20180427072810.GB13269@xz-mi> <20180427095527.GE13269@xz-mi> <20180427114029.GF13269@xz-mi> <20180503060442.GB2378@xz-mi> <547a97a1-0ac0-21b2-af00-036b795b06cc@redhat.com> <20180503072828.GA29580@xz-mi> From: Jason Wang Message-ID: <8cbed1d0-1f4e-db6d-bd83-1042f724827a@redhat.com> Date: Thu, 3 May 2018 15:43:35 +0800 MIME-Version: 1.0 In-Reply-To: <20180503072828.GA29580@xz-mi> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 08/10] intel-iommu: maintain per-device iova ranges List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: "Tian, Kevin" , "Michael S . Tsirkin" , Alex Williamson , Jintack Lim , "qemu-devel@nongnu.org" On 2018=E5=B9=B405=E6=9C=8803=E6=97=A5 15:28, Peter Xu wrote: > On Thu, May 03, 2018 at 03:20:11PM +0800, Jason Wang wrote: >> >> On 2018=E5=B9=B405=E6=9C=8803=E6=97=A5 14:04, Peter Xu wrote: >>> IMHO the guest can't really detect this, but it'll found that the >>> device is not working functionally if it's doing something like what >>> Jason has mentioned. >>> >>> Actually now I have had an idea if we really want to live well even >>> with Jason's example: maybe we'll need to identify PSI/DSI. For DSI, >>> we don't remap for mapped pages; for PSI, we unmap and remap the >>> mapped pages. That'll complicate the stuff a bit, but it should >>> satisfy all the people. >>> >>> Thanks, >> So it looks like there will be still unnecessary unamps. > Could I ask what do you mean by "unecessary unmaps"? It's for "for PSI, we unmap and remap the mapped pages". So for the=20 first "unmap" how do you know it was really necessary without knowing=20 the state of current shadow page table? >> How about record the mappings in the tree too? > As I mentioned, for L1 guest (e.g., DPDK applications running in L1) > it'll be fine. But I'm just afraid we will have other use cases, like > the L2 guests. That might need tons of the mapping entries in the > worst case scenario. > Yes, but that's the price of shadow page tables. Thanks