From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 3/3] megasas: LSI Megaraid SAS emulation Date: Mon, 04 Jul 2011 08:34:37 +0200 Message-ID: <4E115EFD.7020607@redhat.com> References: <1309534555-22178-1-git-send-email-hare@suse.de> <1309534555-22178-2-git-send-email-hare@suse.de> <1309534555-22178-3-git-send-email-hare@suse.de> <1309534555-22178-4-git-send-email-hare@suse.de> <4E0F2215.4040307@suse.de> <4E107E66.3030001@redhat.com> <4E115A21.8010003@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Alexander Graf , qemu-devel@nongnu.org, Stefan Haynoczi , "kvm@vger.kernel.org" To: Hannes Reinecke Return-path: Received: from mx1.redhat.com ([209.132.183.28]:28190 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753038Ab1GDGeq (ORCPT ); Mon, 4 Jul 2011 02:34:46 -0400 In-Reply-To: <4E115A21.8010003@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: On 07/04/2011 08:13 AM, Hannes Reinecke wrote: > On 07/03/2011 04:36 PM, Paolo Bonzini wrote: >> On 07/02/2011 03:50 PM, Hannes Reinecke wrote: >>> (And no, I will not getting into another dog-fight with Paul B. here. >>> Virtio can do without bounce buffers. AHCI can. So I fail to see why >>> SCSI has to rely on bounce buffers.) >> >> I agree, but I do see why a SCSI device might prefer to rely on >> bounce buffers for non-I/O commands. This is why in my last RFC >> series for vmw_pvscsi I let the device choose whether to force a >> bounce buffer or get an external iovec from the HBA. >> > Yes, sure, for non-I/O commands it's perfectly okay. > Most of which will be emulated anyway. > It's bounce buffers for I/O which kills performance. > > But I seem to have missed your last RFC (I'm not reading qemu-devel on a > regular basis ...). > Care to send me a pointer to it? Sure, http://lists.gnu.org/archive/html/qemu-devel/2011-06/msg00668.html Paolo