From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35632) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eb14p-0006Jt-5s for qemu-devel@nongnu.org; Mon, 15 Jan 2018 04:29:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eb14j-0002Q1-D3 for qemu-devel@nongnu.org; Mon, 15 Jan 2018 04:29:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38254) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eb14j-0002PJ-79 for qemu-devel@nongnu.org; Mon, 15 Jan 2018 04:29:05 -0500 References: <2f3d36f8.1ce36.160f49d0471.Coremail.linzc@zju.edu.cn> From: Paolo Bonzini Message-ID: Date: Mon, 15 Jan 2018 10:29:00 +0100 MIME-Version: 1.0 In-Reply-To: <2f3d36f8.1ce36.160f49d0471.Coremail.linzc@zju.edu.cn> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] question about share flatviews List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: CheneyLin , qemu-devel@nongnu.org Cc: aik@ozlabs.ru On 14/01/2018 13:20, CheneyLin wrote: > I'm wondering why we have to shares flatviews between different ASes. I= n > my opinion, arch like=C2=A0x86 only have two ASes(memory AS and io AS),= each > AS is related with only one flatview. Their ASes are definitely differe= nt. Every PCI device has its own AddressSpace. A PCI device's is either the same as the memory AS or the same as the empty AS, hence sharing the FlatView can provide substantial memory usage improvements. Paolo