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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 C5AAAC2BBCD for ; Thu, 17 Dec 2020 11:46:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DBD6238E4 for ; Thu, 17 Dec 2020 11:46:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728074AbgLQLpw (ORCPT ); Thu, 17 Dec 2020 06:45:52 -0500 Received: from foss.arm.com ([217.140.110.172]:59360 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728041AbgLQLpv (ORCPT ); Thu, 17 Dec 2020 06:45:51 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6DF2E31B; Thu, 17 Dec 2020 03:45:05 -0800 (PST) Received: from [10.163.84.19] (unknown [10.163.84.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A06803F66E; Thu, 17 Dec 2020 03:45:01 -0800 (PST) Subject: Re: [PATCH 3/3] s390/mm: Define arch_get_mappable_range() To: David Hildenbrand , Heiko Carstens Cc: linux-mm@kvack.org, akpm@linux-foundation.org, 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 References: <20201210065845.GA20691@osiris> From: Anshuman Khandual Message-ID: <401e72a7-7865-455a-4c7f-79278e3f0af0@arm.com> Date: Thu, 17 Dec 2020 17:15:05 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/10/20 12:34 PM, David Hildenbrand wrote: > >> Am 10.12.2020 um 07:58 schrieb Heiko Carstens : >> >> On Thu, Dec 10, 2020 at 09:48:11AM +0530, Anshuman Khandual wrote: >>>>> Alternatively leaving __segment_load() and vmem_add_memory() unchanged >>>>> will create three range checks i.e two memhp_range_allowed() and the >>>>> existing VMEM_MAX_PHYS check in vmem_add_mapping() on all the hotplug >>>>> paths, which is not optimal. >>>> >>>> Ah, sorry. I didn't follow this discussion too closely. I just thought >>>> my point of view would be clear: let's not have two different ways to >>>> check for the same thing which must be kept in sync. >>>> Therefore I was wondering why this next version is still doing >>>> that. Please find a way to solve this. >>> >>> The following change is after the current series and should work with >>> and without memory hotplug enabled. There will be just a single place >>> i.e vmem_get_max_addr() to update in case the maximum address changes >>> from VMEM_MAX_PHYS to something else later. >> >> Still not. That's way too much code churn for what you want to achieve. >> If the s390 specific patch would look like below you can add >> >> Acked-by: Heiko Carstens >> >> But please make sure that the arch_get_mappable_range() prototype in >> linux/memory_hotplug.h is always visible and does not depend on >> CONFIG_MEMORY_HOTPLUG. I'd like to avoid seeing sparse warnings >> because of this. >> >> Thanks. >> >> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c >> index 77767850d0d0..e0e78234ae57 100644 >> --- a/arch/s390/mm/init.c >> +++ b/arch/s390/mm/init.c >> @@ -291,6 +291,7 @@ int arch_add_memory(int nid, u64 start, u64 size, >> if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot)) >> return -EINVAL; >> >> + VM_BUG_ON(!memhp_range_allowed(start, size, 1)); >> rc = vmem_add_mapping(start, size); >> if (rc) >> return rc; >> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c >> index b239f2ba93b0..ccd55e2f97f9 100644 >> --- a/arch/s390/mm/vmem.c >> +++ b/arch/s390/mm/vmem.c >> @@ -4,6 +4,7 @@ >> * Author(s): Heiko Carstens >> */ >> >> +#include >> #include >> #include >> #include >> @@ -532,11 +533,23 @@ void vmem_remove_mapping(unsigned long start, unsigned long size) >> mutex_unlock(&vmem_mutex); >> } >> >> +struct range arch_get_mappable_range(void) >> +{ >> + struct range range; >> + >> + range.start = 0; >> + range.end = VMEM_MAX_PHYS; >> + return range; >> +} >> + >> int vmem_add_mapping(unsigned long start, unsigned long size) >> { >> + struct range range; >> int ret; >> >> - if (start + size > VMEM_MAX_PHYS || >> + range = arch_get_mappable_range(); >> + if (start < range.start || >> + start + size > range.end || >> start + size < start) >> return -ERANGE; >> >> > > Right, what I had in mind as reply to v1. Not sure if we really need new checks in common code. Having a new memhp_get_pluggable_range() would be sufficient for my use case (virtio-mem). Hello David, Quick question. Currently memhp_get_pluggable_range() is a mm/memory_hotplug.c internal static inline function. Only memhp_range_allowed() is available via the header include/linux/memory_hotplug.h But For memhp_get_pluggable_range() to be visible to the drivers, it needs to get included in the header and also be exported via EXPORT_SYMBOL_GPL() in mm/memory_hotplug.c OR just move the entire definition as static inline into the header itself. Wondering which way would be better ? - Anshuman