From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:46754 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727339AbhAVKn4 (ORCPT ); Fri, 22 Jan 2021 05:43:56 -0500 Subject: Re: [PATCH V3 1/3] mm/memory_hotplug: Prevalidate the address range being added with platform References: <1610975582-12646-1-git-send-email-anshuman.khandual@arm.com> <1610975582-12646-2-git-send-email-anshuman.khandual@arm.com> <9916f217-ec29-33ff-a260-7a26792d23a1@redhat.com> <897c31ba-d3bd-b694-8c87-82e784a60c51@arm.com> From: David Hildenbrand Message-ID: <5e133a5e-41bb-9d6b-f76e-a96d3efe0f5e@redhat.com> Date: Fri, 22 Jan 2021 11:42:17 +0100 MIME-Version: 1.0 In-Reply-To: <897c31ba-d3bd-b694-8c87-82e784a60c51@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit List-ID: To: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org, hca@linux.ibm.com, catalin.marinas@arm.com Cc: Oscar Salvador , Vasily Gorbik , Will Deacon , Ard Biesheuvel , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org On 22.01.21 11:41, Anshuman Khandual wrote: > > On 1/22/21 2:48 PM, David Hildenbrand wrote: >> >>> +/* >>> + * Platforms should define arch_get_mappable_range() that provides >>> + * maximum possible addressable physical memory range for which the >>> + * linear mapping could be created. The platform returned address >>> + * range must adhere to these following semantics. >>> + * >>> + * - range.start <= range.end >>> + * - Range includes both end points [range.start..range.end] >>> + * >>> + * There is also a fallback definition provided here, allowing the >>> + * entire possible physical address range in case any platform does >>> + * not define arch_get_mappable_range(). >>> + */ >>> +struct range __weak arch_get_mappable_range(void) >>> +{ >>> + struct range memhp_range = { >>> + .start = 0UL, >>> + .end = -1ULL, >>> + }; >>> + return memhp_range; >>> +} >>> + >>> +struct range memhp_get_pluggable_range(bool need_mapping) >>> +{ >>> + const u64 max_phys = (1ULL << (MAX_PHYSMEM_BITS + 1)) - 1; >> >> Sorry, thought about that line a bit more, and I think this is just >> wrong (took me longer to realize as it should). The old code used this >> calculation to print the limit only (in a wrong way), let's recap: >> >> Assume MAX_PHYSMEM_BITS=32 >> >> max_phys = (1ULL << (32 + 1)) - 1 = 0x1ffffffffull; >> >> Ehm, these are 33 bit. >> >> OTOH, old code checked for >> >> if (max_addr >> MAX_PHYSMEM_BITS) { >> >> Which makes sense, because >> >> 0x1ffffffffull >> 32 = 1 >> >> results in "true", meaning it's to big, while >> >> 0xffffffffull >> 32 = 0 >> >> correctly results in "false", meaning the address is fine. >> >> >> >> So, this should just be >> >> const u64 max_phys = 1ULL << MAX_PHYSMEM_BITS; >> >> (similarly as calculated in virito-mem code, or in kernel/resource.c) > > Should this be 1ULL << MAX_PHYSMEM_BITS - 1 instead ? Currently there are Yes, obviously, sorry, forgot the -1. -- Thanks, David / dhildenb