From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757080AbcIHGtt (ORCPT ); Thu, 8 Sep 2016 02:49:49 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33914 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756724AbcIHGtr (ORCPT ); Thu, 8 Sep 2016 02:49:47 -0400 Date: Thu, 8 Sep 2016 08:49:43 +0200 From: Ingo Molnar To: Amit Shah Cc: Andy Lutomirski , x86@kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, "Michael S. Tsirkin" Subject: Re: [PATCH] virtio_console: Stop doing DMA on the stack Message-ID: <20160908064943.GA25876@gmail.com> References: <0afe68f9b4be6c95af9e7672b07acd0274c26dfe.1472569320.git.luto@kernel.org> <20160906070343.GD3100@amit-lp.rh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160906070343.GD3100@amit-lp.rh> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Amit Shah wrote: > On (Tue) 30 Aug 2016 [08:04:15], Andy Lutomirski wrote: > > virtio_console uses a small DMA buffer for control requests. Move > > that buffer into heap memory. > > > > Doing virtio DMA on the stack is normally okay on non-DMA-API virtio > > systems (which is currently most of them), but it breaks completely > > if the stack is virtually mapped. > > > > Tested by typing both directions using picocom aimed at /dev/hvc0. > > > > Signed-off-by: Andy Lutomirski > > Looks fine, > > Reviewed-by: Amit Shah > > > --- > > > > Hi all- > > > > This is currently broken in tip:x86/asm. If you (Amit) like this patch, > > would it make sense for Ingo to add it to -tip? > > Yes, I'm fine with that. Thanks! FYI, this patch now lives as: 9472fe7040bb ("virtio_console: Stop doing DMA on the stack") in tip:x86/asm, and is targeted for a v4.9 merge. Thanks, Ingo