Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753249AbaKLRSl (ORCPT ); Wed, 12 Nov 2014 12:18:41 -0500 Received: from mail.emea.novell.com ([130.57.118.101]:40194 "EHLO mail.emea.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753036AbaKLRSj convert rfc822-to-8bit (ORCPT ); Wed, 12 Nov 2014 12:18:39 -0500 Message-Id: <5463A47A0200007800046F19@mail.emea.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.0.1 Date: Wed, 12 Nov 2014 17:18:34 +0000 From: "Jan Beulich" To: "David Vrabel" Cc: , "Thomas Gleixner" , "Greg Kroah-Hartman" , , "BorisOstrovsky" , "Ingo Molnar" , , "H. Peter Anvin" Subject: Re: [Xen-devel] [PATCH 3/3] x86/xen: use the maximum MFN to calculate the required DMA mask References: <1415805906-27316-1-git-send-email-david.vrabel@citrix.com> <1415805906-27316-4-git-send-email-david.vrabel@citrix.com> <546390FC0200007800046E50@mail.emea.novell.com> <546391DE.7040508@citrix.com> In-Reply-To: <546391DE.7040508@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 12.11.14 at 17:59, wrote: > On 12/11/14 15:55, Jan Beulich wrote: >>>>> On 12.11.14 at 16:25, wrote: >>> +u64 >>> +xen_swiotlb_get_required_mask(struct device *dev) >>> +{ >>> + u64 max_mfn; >>> + >>> + max_mfn = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL); >>> + >>> + return DMA_BIT_MASK(fls64(max_mfn << PAGE_SHIFT) + 1); >>> +} >> >> The value the hypercall returns is exclusive and an unsigned long. > > The docs in include/public/memory.h say: > > "Returns the maximum machine frame number of mapped RAM in this system." > > Which sounds inclusive to me... Do we need a doc update here? Possibly - the origin of this is Linux'es mis-named "max_page" I believe. And in any event I'd expect you to base your code changes on reality, not just on documentation... Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/