From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f199.google.com (mail-qt1-f199.google.com [209.85.160.199]) by kanga.kvack.org (Postfix) with ESMTP id 8790E8E00D7 for ; Fri, 25 Jan 2019 14:07:23 -0500 (EST) Received: by mail-qt1-f199.google.com with SMTP id 42so11755614qtr.7 for ; Fri, 25 Jan 2019 11:07:23 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id d19si1767378qke.208.2019.01.25.11.07.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 11:07:22 -0800 (PST) Date: Fri, 25 Jan 2019 14:07:17 -0500 From: Jerome Glisse Subject: Re: [PATCH 2/5] mm/resource: move HMM pr_debug() deeper into resource code Message-ID: <20190125190716.GB3237@redhat.com> References: <20190124231441.37A4A305@viggo.jf.intel.com> <20190124231444.38182DD8@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190124231444.38182DD8@viggo.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, dan.j.williams@intel.com, dave.jiang@intel.com, zwisler@kernel.org, vishal.l.verma@intel.com, thomas.lendacky@amd.com, akpm@linux-foundation.org, mhocko@suse.com, linux-nvdimm@lists.01.org, linux-mm@kvack.org, ying.huang@intel.com, fengguang.wu@intel.com On Thu, Jan 24, 2019 at 03:14:44PM -0800, Dave Hansen wrote: > > From: Dave Hansen > > HMM consumes physical address space for its own use, even > though nothing is mapped or accessible there. It uses a > special resource description (IORES_DESC_DEVICE_PRIVATE_MEMORY) > to uniquely identify these areas. > > When HMM consumes address space, it makes a best guess about > what to consume. However, it is possible that a future memory > or device hotplug can collide with the reserved area. In the > case of these conflicts, there is an error message in > register_memory_resource(). > > Later patches in this series move register_memory_resource() > from using request_resource_conflict() to __request_region(). > Unfortunately, __request_region() does not return the conflict > like the previous function did, which makes it impossible to > check for IORES_DESC_DEVICE_PRIVATE_MEMORY in a conflicting > resource. > > Instead of warning in register_memory_resource(), move the > check into the core resource code itself (__request_region()) > where the conflicting resource _is_ available. This has the > added bonus of producing a warning in case of HMM conflicts > with devices *or* RAM address space, as opposed to the RAM- > only warnings that were there previously. > > Signed-off-by: Dave Hansen > Cc: Dan Williams > Cc: Dave Jiang > Cc: Ross Zwisler > Cc: Vishal Verma > Cc: Tom Lendacky > Cc: Andrew Morton > Cc: Michal Hocko > Cc: linux-nvdimm@lists.01.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: Huang Ying > Cc: Fengguang Wu Reviewed-by: Jerome Glisse > --- > > b/kernel/resource.c | 10 ++++++++++ > b/mm/memory_hotplug.c | 5 ----- > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff -puN kernel/resource.c~move-request_region-check kernel/resource.c > --- a/kernel/resource.c~move-request_region-check 2019-01-24 15:13:14.453199539 -0800 > +++ b/kernel/resource.c 2019-01-24 15:13:14.458199539 -0800 > @@ -1123,6 +1123,16 @@ struct resource * __request_region(struc > conflict = __request_resource(parent, res); > if (!conflict) > break; > + /* > + * mm/hmm.c reserves physical addresses which then > + * become unavailable to other users. Conflicts are > + * not expected. Be verbose if one is encountered. > + */ > + if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) { > + pr_debug("Resource conflict with unaddressable " > + "device memory at %#010llx !\n", > + (unsigned long long)start); > + } > if (conflict != parent) { > if (!(conflict->flags & IORESOURCE_BUSY)) { > parent = conflict; > diff -puN mm/memory_hotplug.c~move-request_region-check mm/memory_hotplug.c > --- a/mm/memory_hotplug.c~move-request_region-check 2019-01-24 15:13:14.455199539 -0800 > +++ b/mm/memory_hotplug.c 2019-01-24 15:13:14.459199539 -0800 > @@ -109,11 +109,6 @@ static struct resource *register_memory_ > res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; > conflict = request_resource_conflict(&iomem_resource, res); > if (conflict) { > - if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) { > - pr_debug("Device unaddressable memory block " > - "memory hotplug at %#010llx !\n", > - (unsigned long long)start); > - } > pr_debug("System RAM resource %pR cannot be added\n", res); > kfree(res); > return ERR_PTR(-EEXIST); > _