From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:12132 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727730AbfGRO1n (ORCPT ); Thu, 18 Jul 2019 10:27:43 -0400 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6IEJCuv095322 for ; Thu, 18 Jul 2019 10:27:42 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2tts6vm9gv-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 18 Jul 2019 10:27:42 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 18 Jul 2019 15:27:40 +0100 Date: Thu, 18 Jul 2019 16:27:35 +0200 From: Halil Pasic Subject: Re: Is __dma_direct_alloc_pages broken on s390? In-Reply-To: <20190718131059.GA18742@infradead.org> References: <20190718091700.353b3721@ezekiel.suse.cz> <20190718113633.GB3581@osiris> <20190718135112.5c65685f@ezekiel.suse.cz> <20190718145044.03dc9804.pasic@linux.ibm.com> <20190718131059.GA18742@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Message-Id: <20190718162735.1559b561.pasic@linux.ibm.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Christoph Hellwig Cc: Petr Tesarik , Heiko Carstens , linux-s390@vger.kernel.org On Thu, 18 Jul 2019 06:10:59 -0700 Christoph Hellwig wrote: > On Thu, Jul 18, 2019 at 02:50:44PM +0200, Halil Pasic wrote: > > > I wondered why the kernel works OK on my system, and it is in fact not > > > so bad. If the first allocation fails, the kernel adds GFP_DMA and > > > retries, so this is not fatal, but with a proper definition of > > > ARCH_ZONE_DMA_BITS it should be possible to get success in the first > > > attempt already, let's do it. > > > > > > Petr T > > > > I fully agree! I will post a patch that provides correct > > ARCH_ZONE_DMA_BITS for s390. > > > > BTW I wonder if ARCH_ZONE_DMA_BITS can be inferred from MAX_DMA_ADDRESS, > > and why do we need both.@Christoph, maybe you can help me understand if > > there is a relationship between the two or not, or? > > MAX_DMA_ADDRESS is a bit of a weird beast which I honestly do not > understand fully, but most of the uses in common code look a little > bogus, and we should probably get rid of it. Thanks! Regards, Halil