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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 3AF98C433FE for ; Mon, 7 Dec 2020 04:40:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0BD120882 for ; Mon, 7 Dec 2020 04:40:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726858AbgLGEjn (ORCPT ); Sun, 6 Dec 2020 23:39:43 -0500 Received: from foss.arm.com ([217.140.110.172]:40494 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726482AbgLGEjm (ORCPT ); Sun, 6 Dec 2020 23:39:42 -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 89F2B1042; Sun, 6 Dec 2020 20:38:56 -0800 (PST) Received: from [10.163.86.92] (unknown [10.163.86.92]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 22C713F718; Sun, 6 Dec 2020 20:38:53 -0800 (PST) Subject: Re: [RFC V2 3/3] s390/mm: Define arch_get_mappable_range() To: David Hildenbrand , Heiko Carstens Cc: linux-mm@kvack.org, akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Vasily Gorbik References: <1606706992-26656-1-git-send-email-anshuman.khandual@arm.com> <1606706992-26656-4-git-send-email-anshuman.khandual@arm.com> <20201202203233.GB11274@osiris> <24905c32-f6c1-97a0-000f-f822b9870ea5@arm.com> <20201203115133.GB9994@osiris> <4d6c9ec4-f1be-46b9-5d67-5c53f5afedc5@redhat.com> From: Anshuman Khandual Message-ID: <62c60c9e-20d6-25bd-94d0-78bfed0f2476@arm.com> Date: Mon, 7 Dec 2020 10:08:49 +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: <4d6c9ec4-f1be-46b9-5d67-5c53f5afedc5@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/3/20 5:31 PM, David Hildenbrand wrote: > On 03.12.20 12:51, Heiko Carstens wrote: >> On Thu, Dec 03, 2020 at 06:03:00AM +0530, Anshuman Khandual wrote: >>>>> diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c >>>>> index 5060956b8e7d..cc055a78f7b6 100644 >>>>> --- a/arch/s390/mm/extmem.c >>>>> +++ b/arch/s390/mm/extmem.c >>>>> @@ -337,6 +337,11 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long >>>>> goto out_free_resource; >>>>> } >>>>> >>>>> + if (seg->end + 1 > VMEM_MAX_PHYS || seg->end + 1 < seg->start_addr) { >>>>> + rc = -ERANGE; >>>>> + goto out_resource; >>>>> + } >>>>> + >>>>> rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1); >>>>> if (rc) >>>>> goto out_resource; >>>>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c >>>>> index b239f2ba93b0..06dddcc0ce06 100644 >>>>> --- a/arch/s390/mm/vmem.c >>>>> +++ b/arch/s390/mm/vmem.c >>>>> @@ -532,14 +532,19 @@ void vmem_remove_mapping(unsigned long start, unsigned long size) >>>>> mutex_unlock(&vmem_mutex); >>>>> } >>>>> >>>>> +struct range arch_get_mappable_range(void) >>>>> +{ >>>>> + struct range memhp_range; >>>>> + >>>>> + memhp_range.start = 0; >>>>> + memhp_range.end = VMEM_MAX_PHYS; >>>>> + return memhp_range; >>>>> +} >>>>> + >>>>> int vmem_add_mapping(unsigned long start, unsigned long size) >>>>> { >>>>> int ret; >>>>> >>>>> - if (start + size > VMEM_MAX_PHYS || >>>>> - start + size < start) >>>>> - return -ERANGE; >>>>> - >>>> >>>> I really fail to see how this could be considered an improvement for >>>> s390. Especially I do not like that the (central) range check is now >>>> moved to the caller (__segment_load). Which would mean potential >>>> additional future callers would have to duplicate that code as well. >>> >>> The physical range check is being moved to the generic hotplug code >>> via arch_get_mappable_range() instead, making the existing check in >>> vmem_add_mapping() redundant. Dropping the check there necessitates >>> adding back a similar check in __segment_load(). Otherwise there >>> will be a loss of functionality in terms of range check. >>> >>> May be we could just keep this existing check in vmem_add_mapping() >>> as well in order avoid this movement but then it would be redundant >>> check in every hotplug path. >>> >>> So I guess the choice is to either have redundant range checks in >>> all hotplug paths or future internal callers of vmem_add_mapping() >>> take care of the range check. >> >> The problem I have with this current approach from an architecture >> perspective: we end up having two completely different methods which >> are doing the same and must be kept in sync. This might be obvious >> looking at this patch, but I'm sure this will go out-of-sync (aka >> broken) sooner or later. > > Exactly, there should be one function only that was the whole idea of > arch_get_mappable_range(). > >> >> Therefore I would really like to see a single method to do the range >> checking. Maybe you could add a callback into architecture code, so >> that such an architecture specific function could also be used >> elsewhere. Dunno. >> > > I think we can just switch to using "memhp_range_allowed()" here then > after implementing arch_get_mappable_range(). > > Doesn't hurt to double check in vmem_add_mapping() - especially to keep > extmem working without changes. At least for callers of memory hotplug > it's then clear which values actually won't fail deep down in arch code. But there is a small problem here. memhp_range_allowed() is now defined and available with CONFIG_MEMORY_HOTPLUG where as vmem_add_mapping() and __segment_load() are generally available without any config dependency. So if CONFIG_MEMORY_HOTPLUG is not enabled there will be a build failure in vmem_add_mapping() for memhp_range_allowed() symbol. We could just move VM_BUG_ON(!memhp_range_allowed(start, size, 1)) check from vmem_add_mapping() to arch_add_memory() like on arm64 platform. But then __segment_load() would need that additional new check to compensate as proposed earlier. Also leaving vmem_add_mapping() and __segment_load() unchanged will cause the address range check to be called three times on the hotplug path i.e 1. register_memory_resource() 2. arch_add_memory() 3. vmem_add_mapping() Moving memhp_range_allowed() check inside arch_add_memory() seems better and consistent with arm64. Also in the future, any platform which choose to override arch_get_mappable() will have this additional VM_BUG_ON() in their arch_add_memory(). 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=-10.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 12351C433FE for ; Mon, 7 Dec 2020 04:40:20 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BB6F620882 for ; Mon, 7 Dec 2020 04:40:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB6F620882 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=rLPLbG81yLf73PyKwWuFoZTcchiq1SClWw5E5E6sUOY=; b=oUagDaif1tC5SeCG2a8hawyKr CoeX/aCm6FhQGsOaORTZxaIg3URM0tCkZ/PgsyVwsh4/mPTEzM61bZoN5KTqSJt7yRq2qxIUKq0OM jFwS5YFNFNhay7kliX4C3jpJZQLl8VHUAYqAYAPUKFMMDFdd+k9ucKx8ss9xHwfEOVhvKynWKSJBs 38P0xSzcYHJAP3Ba9xE2N0PAU305a7ZOtiQih0yz4Ve3qBXOGC49kpasgMY6g7XT98ezSnJeyaWZf kosuSZnWZFUPbmtWysdScK82JC0DZLDZ7wWNUMZsxGQEu1j4GMjsX8950eiLIazuhX0ck5RHQ2rUg q3dgS0qDQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1km8Ig-0002CV-9Q; Mon, 07 Dec 2020 04:39:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1km8Ie-0002Bi-DH for linux-arm-kernel@lists.infradead.org; Mon, 07 Dec 2020 04:39:01 +0000 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 89F2B1042; Sun, 6 Dec 2020 20:38:56 -0800 (PST) Received: from [10.163.86.92] (unknown [10.163.86.92]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 22C713F718; Sun, 6 Dec 2020 20:38:53 -0800 (PST) Subject: Re: [RFC V2 3/3] s390/mm: Define arch_get_mappable_range() To: David Hildenbrand , Heiko Carstens References: <1606706992-26656-1-git-send-email-anshuman.khandual@arm.com> <1606706992-26656-4-git-send-email-anshuman.khandual@arm.com> <20201202203233.GB11274@osiris> <24905c32-f6c1-97a0-000f-f822b9870ea5@arm.com> <20201203115133.GB9994@osiris> <4d6c9ec4-f1be-46b9-5d67-5c53f5afedc5@redhat.com> From: Anshuman Khandual Message-ID: <62c60c9e-20d6-25bd-94d0-78bfed0f2476@arm.com> Date: Mon, 7 Dec 2020 10:08:49 +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: <4d6c9ec4-f1be-46b9-5d67-5c53f5afedc5@redhat.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201206_233900_547123_99613187 X-CRM114-Status: GOOD ( 27.62 ) 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: linux-s390@vger.kernel.org, Vasily Gorbik , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org 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 On 12/3/20 5:31 PM, David Hildenbrand wrote: > On 03.12.20 12:51, Heiko Carstens wrote: >> On Thu, Dec 03, 2020 at 06:03:00AM +0530, Anshuman Khandual wrote: >>>>> diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c >>>>> index 5060956b8e7d..cc055a78f7b6 100644 >>>>> --- a/arch/s390/mm/extmem.c >>>>> +++ b/arch/s390/mm/extmem.c >>>>> @@ -337,6 +337,11 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long >>>>> goto out_free_resource; >>>>> } >>>>> >>>>> + if (seg->end + 1 > VMEM_MAX_PHYS || seg->end + 1 < seg->start_addr) { >>>>> + rc = -ERANGE; >>>>> + goto out_resource; >>>>> + } >>>>> + >>>>> rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1); >>>>> if (rc) >>>>> goto out_resource; >>>>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c >>>>> index b239f2ba93b0..06dddcc0ce06 100644 >>>>> --- a/arch/s390/mm/vmem.c >>>>> +++ b/arch/s390/mm/vmem.c >>>>> @@ -532,14 +532,19 @@ void vmem_remove_mapping(unsigned long start, unsigned long size) >>>>> mutex_unlock(&vmem_mutex); >>>>> } >>>>> >>>>> +struct range arch_get_mappable_range(void) >>>>> +{ >>>>> + struct range memhp_range; >>>>> + >>>>> + memhp_range.start = 0; >>>>> + memhp_range.end = VMEM_MAX_PHYS; >>>>> + return memhp_range; >>>>> +} >>>>> + >>>>> int vmem_add_mapping(unsigned long start, unsigned long size) >>>>> { >>>>> int ret; >>>>> >>>>> - if (start + size > VMEM_MAX_PHYS || >>>>> - start + size < start) >>>>> - return -ERANGE; >>>>> - >>>> >>>> I really fail to see how this could be considered an improvement for >>>> s390. Especially I do not like that the (central) range check is now >>>> moved to the caller (__segment_load). Which would mean potential >>>> additional future callers would have to duplicate that code as well. >>> >>> The physical range check is being moved to the generic hotplug code >>> via arch_get_mappable_range() instead, making the existing check in >>> vmem_add_mapping() redundant. Dropping the check there necessitates >>> adding back a similar check in __segment_load(). Otherwise there >>> will be a loss of functionality in terms of range check. >>> >>> May be we could just keep this existing check in vmem_add_mapping() >>> as well in order avoid this movement but then it would be redundant >>> check in every hotplug path. >>> >>> So I guess the choice is to either have redundant range checks in >>> all hotplug paths or future internal callers of vmem_add_mapping() >>> take care of the range check. >> >> The problem I have with this current approach from an architecture >> perspective: we end up having two completely different methods which >> are doing the same and must be kept in sync. This might be obvious >> looking at this patch, but I'm sure this will go out-of-sync (aka >> broken) sooner or later. > > Exactly, there should be one function only that was the whole idea of > arch_get_mappable_range(). > >> >> Therefore I would really like to see a single method to do the range >> checking. Maybe you could add a callback into architecture code, so >> that such an architecture specific function could also be used >> elsewhere. Dunno. >> > > I think we can just switch to using "memhp_range_allowed()" here then > after implementing arch_get_mappable_range(). > > Doesn't hurt to double check in vmem_add_mapping() - especially to keep > extmem working without changes. At least for callers of memory hotplug > it's then clear which values actually won't fail deep down in arch code. But there is a small problem here. memhp_range_allowed() is now defined and available with CONFIG_MEMORY_HOTPLUG where as vmem_add_mapping() and __segment_load() are generally available without any config dependency. So if CONFIG_MEMORY_HOTPLUG is not enabled there will be a build failure in vmem_add_mapping() for memhp_range_allowed() symbol. We could just move VM_BUG_ON(!memhp_range_allowed(start, size, 1)) check from vmem_add_mapping() to arch_add_memory() like on arm64 platform. But then __segment_load() would need that additional new check to compensate as proposed earlier. Also leaving vmem_add_mapping() and __segment_load() unchanged will cause the address range check to be called three times on the hotplug path i.e 1. register_memory_resource() 2. arch_add_memory() 3. vmem_add_mapping() Moving memhp_range_allowed() check inside arch_add_memory() seems better and consistent with arm64. Also in the future, any platform which choose to override arch_get_mappable() will have this additional VM_BUG_ON() in their arch_add_memory(). _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel