From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38288) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ur9lG-0006fr-LU for qemu-devel@nongnu.org; Mon, 24 Jun 2013 12:37:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ur9lE-0007w5-3t for qemu-devel@nongnu.org; Mon, 24 Jun 2013 12:37:02 -0400 Received: from mx.ipv6.kamp.de ([2a02:248:0:51::16]:49784 helo=mx01.kamp.de) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1Ur9lD-0007vy-Qg for qemu-devel@nongnu.org; Mon, 24 Jun 2013 12:37:00 -0400 Message-ID: <51C875A8.6060909@kamp.de> Date: Mon, 24 Jun 2013 18:36:56 +0200 From: Peter Lieven MIME-Version: 1.0 References: <1371934712-11714-1-git-send-email-pl@kamp.de> <1371934712-11714-8-git-send-email-pl@kamp.de> <51C85808.7000206@redhat.com> <51C86F7D.401@kamp.de> <51C87011.7080404@redhat.com> <51C872B4.9050301@kamp.de> <51C87370.7060802@redhat.com> In-Reply-To: <51C87370.7060802@redhat.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Kevin Wolf , ronniesahlberg@gmail.com, qemu-devel@nongnu.org, Stefan Hajnoczi Am 24.06.2013 18:27, schrieb Paolo Bonzini: > Il 24/06/2013 18:24, Peter Lieven ha scritto: >>>> So far, 4K blocksize is usable if you also specify the same block size >>>> for the guest device. I have posted once the patches to do >>>> read-modify-write, but I never really pursued inclusion of those. >>>> >>>> In any case, the right place to fix this is the block layer; >>>> driver-specific hacks are... hacks. :) >> Where do I find the sector size if not in BDRV_SECTOR_SIZE? >> Is there a dynamic field or is the answer qemu only support 512 Byte >> sector size at the moment? > bdrv_read/write and friends are always in 512-byte units. > > There is bs->buffer_alignment for the guest sector size, but it is not > set at bdrv_open, only later. So I think QEMU support for bigger > sectors is too sparse to be useful. > >> So you would go for fail to open a device if the LUN blocksize is >> not equal to BDRV_SECTOR_SIZE? > Either that, or fails reads/writes that are not aligned. It would be the easiest. Maybe Ronnie can point out what the hack with the acb->buffer_offset in aio_read was meant for. All other functions have the requirement to be properly aligned regarding to the xfersize. I am also not sure if the e.g. reading of 512 byte at sector 0 from a 4K block device does still work with the iovector patches we added earlier. Peter > > Paolo