From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51536) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VEnwA-0000ZX-4X for qemu-devel@nongnu.org; Wed, 28 Aug 2013 18:10:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VEnw1-0002FL-8v for qemu-devel@nongnu.org; Wed, 28 Aug 2013 18:10:02 -0400 Received: from terminus.zytor.com ([2001:1868:205::10]:49737) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VEnw0-00021I-QZ for qemu-devel@nongnu.org; Wed, 28 Aug 2013 18:09:53 -0400 Message-ID: <521E6555.9010400@zytor.com> Date: Wed, 28 Aug 2013 14:02:13 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 References: <20130828080723.GD4696@stefanha-thinkpad.muc.redhat.com> <521DE2DF.70707@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Stefan Hajnoczi , "rusty@rustcorp.com.au" , "qemu-devel@nongnu.org" , Stefan Hajnoczi , "Xie, Huawei" , Laszlo Ersek On 08/28/2013 10:35 AM, Anthony Liguori wrote: > Yes, it was originally designed with the 16TB limit in mind. > > PCI doesn't support 64-bit PIO operations so it would have required a > high/low register and additional magic. > s/PCI/x86/ "Additional magic" is needed only if atomic changes are necessary, but in this case this is stuff that is set up during early configuration and so isn't an issue. The "additional magic" needed in that case is latch logic - the write to the low part doesn't actually take effect until the high part is written. -hpa