From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933562AbeB1PsX (ORCPT ); Wed, 28 Feb 2018 10:48:23 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:53320 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933530AbeB1PsR (ORCPT ); Wed, 28 Feb 2018 10:48:17 -0500 Date: Wed, 28 Feb 2018 17:48:11 +0200 From: "Michael S. Tsirkin" To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Cc: Linux Kernel Mailing List , Sergio Lopez Pascual , Baoquan He , "Somlo, Gabriel" , xiaolong.ye@intel.com Subject: Re: [PATCH v15 11/11] RFC: fw_cfg: do DMA read operation Message-ID: <20180228174635-mutt-send-email-mst@kernel.org> References: <20180215213312.29234-1-marcandre.lureau@redhat.com> <20180215213312.29234-12-marcandre.lureau@redhat.com> <20180227020104-mutt-send-email-mst@kernel.org> <20180228173444-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 28, 2018 at 04:41:51PM +0100, Marc-André Lureau wrote: > I don't know if it's always safe to enable dma in read_raw(), how > could we know? Is there a check we could use to choose one or ther > other (and thus avoiding explicit dma/readfn argument)? I'm not sure - but does it really matter? Is anyone reading large files like this in production where speed matters? Why even bother with DMA? -- MST