From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.110.172]:37766 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729843AbgLBMQn (ORCPT ); Wed, 2 Dec 2020 07:16:43 -0500 Subject: Re: [RFC V2 1/3] mm/hotplug: Prevalidate the address range being added with platform References: <1606706992-26656-1-git-send-email-anshuman.khandual@arm.com> <1606706992-26656-2-git-send-email-anshuman.khandual@arm.com> <864c701a-4391-f768-1b95-1992e21835a2@redhat.com> From: Anshuman Khandual Message-ID: <349f7b33-cd5b-4240-e7c0-d8ad39c8ba71@arm.com> Date: Wed, 2 Dec 2020 17:45:39 +0530 MIME-Version: 1.0 In-Reply-To: <864c701a-4391-f768-1b95-1992e21835a2@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit List-ID: To: David Hildenbrand , linux-mm@kvack.org, akpm@linux-foundation.org Cc: linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org On 12/2/20 2:50 PM, David Hildenbrand wrote: > On 30.11.20 04:29, Anshuman Khandual wrote: >> This introduces memhp_range_allowed() which can be called in various memory >> hotplug paths to prevalidate the address range which is being added, with >> the platform. Then memhp_range_allowed() calls memhp_get_pluggable_range() >> which provides applicable address range depending on whether linear mapping >> is required or not. For ranges that require linear mapping, it calls a new >> arch callback arch_get_mappable_range() which the platform can override. So >> the new callback, in turn provides the platform an opportunity to configure >> acceptable memory hotplug address ranges in case there are constraints. >> >> This mechanism will help prevent platform specific errors deep down during >> hotplug calls. This drops now redundant check_hotplug_memory_addressable() >> check in __add_pages(). >> > > > [...] > >> /* >> * Reasonably generic function for adding memory. It is >> * expected that archs that support memory hotplug will >> @@ -317,10 +304,6 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, >> if (WARN_ON_ONCE(!params->pgprot.pgprot)) >> return -EINVAL; >> >> - err = check_hotplug_memory_addressable(pfn, nr_pages); >> - if (err) >> - return err; >> - > > I was wondering if we should add a VM_BUG_ON(!memhp_range_allowed()) > here to make it clearer that callers are expected to check that first. > Maybe an other places as well (e.g., arch code where we remove the > original checks) Makes sense, will add them. > > [...] > > >> #endif /* CONFIG_MEMORY_HOTREMOVE */ >> diff --git a/mm/memremap.c b/mm/memremap.c >> index 16b2fb482da1..26c1825756cc 100644 >> --- a/mm/memremap.c >> +++ b/mm/memremap.c >> @@ -185,6 +185,7 @@ static void dev_pagemap_percpu_release(struct percpu_ref *ref) >> static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params, >> int range_id, int nid) >> { >> + const bool is_private = pgmap->type == MEMORY_DEVICE_PRIVATE; >> struct range *range = &pgmap->ranges[range_id]; >> struct dev_pagemap *conflict_pgmap; >> int error, is_ram; >> @@ -230,6 +231,9 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params, >> if (error) >> goto err_pfn_remap; >> >> + if (!memhp_range_allowed(range->start, range_len(range), !is_private)) >> + goto err_pfn_remap; >> + >> mem_hotplug_begin(); >> >> /* >> @@ -243,7 +247,7 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params, >> * the CPU, we do want the linear mapping and thus use >> * arch_add_memory(). >> */ >> - if (pgmap->type == MEMORY_DEVICE_PRIVATE) { >> + if (is_private) { >> error = add_pages(nid, PHYS_PFN(range->start), >> PHYS_PFN(range_len(range)), params); >> } else { >> > > In general, LGTM. > Okay