From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.110.172]:58490 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725873AbhAMFEg (ORCPT ); Wed, 13 Jan 2021 00:04:36 -0500 Subject: Re: [PATCH V2 1/3] mm/hotplug: Prevalidate the address range being added with platform References: <1608218912-28932-1-git-send-email-anshuman.khandual@arm.com> <1608218912-28932-2-git-send-email-anshuman.khandual@arm.com> <10e733fa-4568-d38f-9b95-2ccc5dc627b8@redhat.com> <20210111134303.GA3031@linux> <556a8a62-7bb2-d16b-67ea-57c87c1a6aa7@redhat.com> From: Anshuman Khandual Message-ID: <041d9344-b07c-c6f9-c41a-01057470c350@arm.com> Date: Wed, 13 Jan 2021 10:34:04 +0530 MIME-Version: 1.0 In-Reply-To: <556a8a62-7bb2-d16b-67ea-57c87c1a6aa7@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit List-ID: To: David Hildenbrand , Oscar Salvador Cc: linux-mm@kvack.org, akpm@linux-foundation.org, hca@linux.ibm.com, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Vasily Gorbik , Will Deacon , Ard Biesheuvel , Mark Rutland On 1/12/21 3:39 PM, David Hildenbrand wrote: > On 12.01.21 04:51, Anshuman Khandual wrote: >> >> >> On 1/11/21 7:13 PM, Oscar Salvador wrote: >>> On Mon, Jan 11, 2021 at 11:51:47AM +0100, David Hildenbrand wrote: >>>> AFAIKs, all memhp_get_pluggable_range() users pass "1". >>>> >>>> What about the "add_pages()-only" path? >>> >>> I guess you refer to memremap_pages(), right? >> >> Right, via pagemap_range(). >> >>> If so, moving the added memhp_range_allowed() check above the if-else might do >>> the trick >>> >> We had that code in the earlier version. But dropped it, as we did >> not want to add any new checks in the generic code. Can add it back >> if that is preferred. > > I remember discussing replacing the check in __add_pages() instead. But The proposed change for __add_pages() now seems misleading. Instead of VM_BUG_ON(), memhp_range_allowed() should be checked directly for a non linear mapping i.e with 'false' argument and return prematurely in case that check fails. s/VM_BUG_ON(!memhp_range_allowed(.., 1)/!memhp_range_allowed(.., 0)/ /* * Reasonably generic function for adding memory. It is * expected that archs that support memory hotplug will @@ -317,10 +304,7 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, if (WARN_ON_ONCE(!params->pgprot.pgprot)) return -EINVAL; - err = check_hotplug_memory_addressable(pfn, nr_pages); - if (err) - return err; - + VM_BUG_ON(!memhp_range_allowed(PFN_PHYS(pfn), nr_pages * PAGE_SIZE, 1)); if (altmap) { /* * Validate altmap is within bounds of the total request @@ -1181,6 +1165,61 @@ int add_memory_driver_managed(int nid, u64 start, u64 size, > I don't really care where the check ends up being. As discussed, at some > point, we should provide versions of add_pages() and arch_add_pages() > that don't immediately end in arch-code. Sure. But for now, AFAICS the above replacement should be sufficient.