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Fri, 22 Jan 2021 10:43:29 +0000 (UTC) Received: from [10.36.114.142] (ovpn-114-142.ams2.redhat.com [10.36.114.142]) by smtp.corp.redhat.com (Postfix) with ESMTP id 845805D9CA; Fri, 22 Jan 2021 10:43:26 +0000 (UTC) Subject: Re: [PATCH V3 1/3] mm/memory_hotplug: Prevalidate the address range being added with platform From: David Hildenbrand 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 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> <5e133a5e-41bb-9d6b-f76e-a96d3efe0f5e@redhat.com> Organization: Red Hat GmbH Message-ID: <417b574c-309e-6d5d-36e4-9b16d82c54a6@redhat.com> Date: Fri, 22 Jan 2021 11:43:25 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <5e133a5e-41bb-9d6b-f76e-a96d3efe0f5e@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 22.01.21 11:42, David Hildenbrand wrote: > 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. > const u64 max_phys = (1ULL << MAX_PHYSMEM_BITS) - 1; to be precise. -- Thanks, David / dhildenb