From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by kanga.kvack.org (Postfix) with ESMTP id 428C68E0002 for ; Wed, 16 Jan 2019 14:16:45 -0500 (EST) Received: by mail-qt1-f200.google.com with SMTP id n39so6504417qtn.18 for ; Wed, 16 Jan 2019 11:16:45 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id o5si1711136qta.399.2019.01.16.11.16.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 16 Jan 2019 11:16:42 -0800 (PST) Date: Wed, 16 Jan 2019 14:16:36 -0500 From: Jerome Glisse Subject: Re: [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children Message-ID: <20190116191635.GD3617@redhat.com> References: <20190116181859.D1504459@viggo.jf.intel.com> <20190116181902.670EEBC3@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190116181902.670EEBC3@viggo.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: dave@sr71.net, 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-kernel@vger.kernel.org, linux-mm@kvack.org, ying.huang@intel.com, fengguang.wu@intel.com, bp@suse.de, bhelgaas@google.com, baiyaowei@cmss.chinamobile.com, tiwai@suse.de On Wed, Jan 16, 2019 at 10:19:02AM -0800, Dave Hansen wrote: > > From: Dave Hansen > > The mm/resource.c code is used to manage the physical address > space. We can view the current resource configuration in > /proc/iomem. An example of this is at the bottom of this > description. > > The nvdimm subsystem "owns" the physical address resources which > map to persistent memory and has resources inserted for them as > "Persistent Memory". We want to use this persistent memory, but > as volatile memory, just like RAM. The best way to do this is > to leave the existing resource in place, but add a "System RAM" > resource underneath it. This clearly communicates the ownership > relationship of this memory. > > The request_resource_conflict() API only deals with the > top-level resources. Replace it with __request_region() which > will search for !IORESOURCE_BUSY areas lower in the resource > tree than the top level. > > We also rework the old error message a bit since we do not get > the conflicting entry back: only an indication that we *had* a > conflict. We should keep the device private check (moving it in __request_region) as device private can try to register un-use physical address (un-use at time of device private registration) that latter can block valid physical address the error message you are removing report such event. > > We *could* also simply truncate the existing top-level > "Persistent Memory" resource and take over the released address > space. But, this means that if we ever decide to hot-unplug the > "RAM" and give it back, we need to recreate the original setup, > which may mean going back to the BIOS tables. > > This should have no real effect on the existing collision > detection because the areas that truly conflict should be marked > IORESOURCE_BUSY. Still i am worrying that this might allow device private to register itself as a child of some un-busy resource as this patch obviously change the behavior of register_memory_resource() What about instead explicitly providing parent resource to add_memory() and then to register_memory_resource() so if it is provided as an argument (!NULL) then you can __request_region(arg_res, ...) otherwise you keep existing code intact ? Cheers, Jérôme > > 00000000-00000fff : Reserved > 00001000-0009fbff : System RAM > 0009fc00-0009ffff : Reserved > 000a0000-000bffff : PCI Bus 0000:00 > 000c0000-000c97ff : Video ROM > 000c9800-000ca5ff : Adapter ROM > 000f0000-000fffff : Reserved > 000f0000-000fffff : System ROM > 00100000-9fffffff : System RAM > 01000000-01e071d0 : Kernel code > 01e071d1-027dfdff : Kernel data > 02dc6000-0305dfff : Kernel bss > a0000000-afffffff : Persistent Memory (legacy) > a0000000-a7ffffff : System RAM > b0000000-bffdffff : System RAM > bffe0000-bfffffff : Reserved > c0000000-febfffff : PCI Bus 0000:00 > > 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 > > Signed-off-by: Dave Hansen > --- > > b/mm/memory_hotplug.c | 31 ++++++++++++++----------------- > 1 file changed, 14 insertions(+), 17 deletions(-) > > diff -puN mm/memory_hotplug.c~mm-memory-hotplug-allow-memory-resource-to-be-child mm/memory_hotplug.c > --- a/mm/memory_hotplug.c~mm-memory-hotplug-allow-memory-resource-to-be-child 2018-12-20 11:48:42.317771933 -0800 > +++ b/mm/memory_hotplug.c 2018-12-20 11:48:42.322771933 -0800 > @@ -98,24 +98,21 @@ void mem_hotplug_done(void) > /* add this memory to iomem resource */ > static struct resource *register_memory_resource(u64 start, u64 size) > { > - struct resource *res, *conflict; > - res = kzalloc(sizeof(struct resource), GFP_KERNEL); > - if (!res) > - return ERR_PTR(-ENOMEM); > + struct resource *res; > + unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; > + char *resource_name = "System RAM"; > > - res->name = "System RAM"; > - res->start = start; > - res->end = start + size - 1; > - 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); > + /* > + * Request ownership of the new memory range. This might be > + * a child of an existing resource that was present but > + * not marked as busy. > + */ > + res = __request_region(&iomem_resource, start, size, > + resource_name, flags); > + > + if (!res) { > + pr_debug("Unable to reserve System RAM region: %016llx->%016llx\n", > + start, start + size); > return ERR_PTR(-EEXIST); > } > return res; > _ >