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Fri, 22 Jan 2021 09:18:24 +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 E8B6010023B9; Fri, 22 Jan 2021 09:18:21 +0000 (UTC) Subject: Re: [PATCH V3 1/3] mm/memory_hotplug: Prevalidate the address range being added with platform To: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org, hca@linux.ibm.com, catalin.marinas@arm.com References: <1610975582-12646-1-git-send-email-anshuman.khandual@arm.com> <1610975582-12646-2-git-send-email-anshuman.khandual@arm.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <9916f217-ec29-33ff-a260-7a26792d23a1@redhat.com> Date: Fri, 22 Jan 2021 10:18:21 +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: <1610975582-12646-2-git-send-email-anshuman.khandual@arm.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210122_041831_873372_DBEBF730 X-CRM114-Status: GOOD ( 20.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-s390@vger.kernel.org, Vasily Gorbik , linux-kernel@vger.kernel.org, Will Deacon , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, Oscar Salvador Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > +/* > + * 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) > + struct range memhp_range; > + > + if (need_mapping) { > + memhp_range = arch_get_mappable_range(); > + if (memhp_range.start > max_phys) { > + memhp_range.start = 0; > + memhp_range.end = 0; > + } > + memhp_range.end = min_t(u64, memhp_range.end, max_phys); > + } else { > + memhp_range.start = 0; > + memhp_range.end = max_phys; > + } > + return memhp_range; > +} > +EXPORT_SYMBOL_GPL(memhp_get_pluggable_range); -- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel