From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 342D2C282C5 for ; Wed, 23 Jan 2019 17:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0234821855 for ; Wed, 23 Jan 2019 17:05:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548263125; bh=OmNg+ClXWmRx2IRdzYBMnQ7ZUoaJHZ35h2gI2F41Zzo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=RQwBEidB2VCFEeTi5eSciEX5MLiAeubpsIZCGxV7orBi+mPDJW0oaMJOd4/wHky42 gRRM4YzN4EqIdkw87I/e3+QZCAbAlXWgj81GBB5DK0ZcHOnAk4CJWJUL8u/284/PdS 2JR9ltPOpjA13C4uZ4rFRcFtejq72uo3Ji0o5jc4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726849AbfAWRFX (ORCPT ); Wed, 23 Jan 2019 12:05:23 -0500 Received: from mx2.suse.de ([195.135.220.15]:60416 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725996AbfAWRFW (ORCPT ); Wed, 23 Jan 2019 12:05:22 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A9832B06E; Wed, 23 Jan 2019 17:05:20 +0000 (UTC) Date: Wed, 23 Jan 2019 18:05:18 +0100 From: Michal Hocko 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, 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 Subject: Re: [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children Message-ID: <20190123170518.GC4087@dhcp22.suse.cz> References: <20190116181859.D1504459@viggo.jf.intel.com> <20190116181902.670EEBC3@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190116181902.670EEBC3@viggo.jf.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Sorry for a late reply] On Wed 16-01-19 10:19:02, 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 *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. > > 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 This is the only memory hotplug related change in this series AFAICS. Unfortunately I am not really familiar with guts for resources infrastructure so I cannot judge the correctness. The change looks sensible to me although I do not feel like acking it. Overall design of this feature makes a lot of sense to me. It doesn't really add any weird APIs yet it allows to use nvdimms as a memory transparently. All future policies are to be defined by the userspace and I like that. I was especially astonished by the sheer size of the driver and changes it required to achieve that. Really nice! > 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; > _ -- Michal Hocko SUSE Labs