From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755892Ab3AIA61 (ORCPT ); Tue, 8 Jan 2013 19:58:27 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:46285 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754790Ab3AIA6Z (ORCPT ); Tue, 8 Jan 2013 19:58:25 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Konrad Rzeszutek Wilk Cc: Yinghai Lu , Shuah Khan , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andrew Morton , Borislav Petkov , Jan Kiszka , Jason Wessel , linux-kernel@vger.kernel.org, Joerg Roedel References: <20130107152622.GD3219@phenom.dumpdata.com> <8762382z2c.fsf@xmission.com> <87y5g4z7rp.fsf@xmission.com> <20130109004340.GA12234@konrad-lan.dumpdata.com> Date: Tue, 08 Jan 2013 16:58:14 -0800 In-Reply-To: <20130109004340.GA12234@konrad-lan.dumpdata.com> (Konrad Rzeszutek Wilk's message of "Tue, 8 Jan 2013 19:43:41 -0500") Message-ID: <87txqruq8p.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX18cragcPHpiOGeOL8lYV5ys0pKuWZFGkn4= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 2.9 KHOP_BIG_TO_CC Sent to 10+ recipients instaed of Bcc or a list * 3.0 XMDrug1234561 Drug references * 0.1 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0001] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.1 XMSolicitRefs_0 Weightloss drug X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **;Konrad Rzeszutek Wilk X-Spam-Relay-Country: Subject: Re: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is not enough ram for it X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 14 Nov 2012 14:26:46 -0700) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Konrad Rzeszutek Wilk writes: > On Tue, Jan 08, 2013 at 03:40:11PM -0800, Yinghai Lu wrote: >> On Mon, Jan 7, 2013 at 7:50 PM, Yinghai Lu wrote: >> > On Mon, Jan 7, 2013 at 7:13 PM, Eric W. Biederman wrote: >> >> I meant we should detect failure to allocate bounce buffers in in >> >> swiotlb_init() instead of panicing. >> >> >> >> I meant swiotlb_map_single() should either panic or simply fail. >> >> >> >> If I have read lib/swiotlb.c correctly the only place we allocate a >> >> bounce buffer is in swiotlb_map_single. If there are more places we can >> >> allocate bounce buffers those need to be handled as well. >> > >> > ok, will give it a try. >> >> please check if you are ok with attached. >> >> looks like it need more change of lines. > > The swiotlb_full check I don't believe is neccessary. You won't ever get > to that unless swiotlb_map_page has at least provided a bounce buffer. > And if the swiotlb_map_page does not have a bounce buffer it will exit > with: > > + if (no_iotlb_memory) > + return SWIOTLB_MAP_ERROR; > + > > which is dangerous. That is b/c there are drivers that don't use the > dma_mapping_error check (so check the bus address after calling > pci_map_*). This means they would try to do DMA on 0xffffffff (yikes!). > > That is reason the failback (v_overflow_buffer) is still in > usage - b/c we have drivers that might just do this and this is the last > resort for them. And until those drivers are fixed - we _need_ this > fallback to work. So instead we need to say? + if (no_iotlb_memory) + panic("Cannot allocate SWIOTLB buffer"); + Which is just making the panic a little later than it used to be and seems completely reasonable. Eric