Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932427AbcKRRSA (ORCPT ); Fri, 18 Nov 2016 12:18:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33724 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932358AbcKRRRt (ORCPT ); Fri, 18 Nov 2016 12:17:49 -0500 From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= To: akpm@linux-foundation.org, , linux-mm@kvack.org Cc: John Hubbard , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Subject: [HMM v13 07/18] mm/ZONE_DEVICE/x86: add support for un-addressable device memory Date: Fri, 18 Nov 2016 13:18:16 -0500 Message-Id: <1479493107-982-8-git-send-email-jglisse@redhat.com> In-Reply-To: <1479493107-982-1-git-send-email-jglisse@redhat.com> References: <1479493107-982-1-git-send-email-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 18 Nov 2016 17:17:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2346 Lines: 71 It does not need much, just skip populating kernel linear mapping for range of un-addressable device memory (it is pick so that there is no physical memory resource overlapping it). All the logic is in share mm code. Only support x86-64 as this feature doesn't make much sense with constrained virtual address space of 32bits architecture. Signed-off-by: Jérôme Glisse Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" --- arch/x86/mm/init_64.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 8c4abb0..556f7bb 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -661,13 +661,17 @@ int arch_add_memory(int nid, u64 start, u64 size, int flags) unsigned long nr_pages = size >> PAGE_SHIFT; int ret; - /* Need to add support for device and unaddressable memory if needed */ - if (flags & MEMORY_UNADDRESSABLE) { - BUG(); - return -EINVAL; - } - - init_memory_mapping(start, start + size); + /* + * We get un-addressable memory when some one is adding a ZONE_DEVICE + * to have struct page for a device memory which is not accessible by + * the CPU so it is pointless to have a linear kernel mapping of such + * memory. + * + * Core mm should make sure it never set a pte pointing to such fake + * physical range. + */ + if (!(flags & MEMORY_UNADDRESSABLE)) + init_memory_mapping(start, start + size); ret = __add_pages(nid, zone, start_pfn, nr_pages); WARN_ON_ONCE(ret); @@ -972,12 +976,6 @@ int __ref arch_remove_memory(u64 start, u64 size, int flags) struct zone *zone; int ret; - /* Need to add support for device and unaddressable memory if needed */ - if (flags & MEMORY_UNADDRESSABLE) { - BUG(); - return -EINVAL; - } - /* With altmap the first mapped page is offset from @start */ altmap = to_vmem_altmap((unsigned long) page); if (altmap) @@ -985,7 +983,9 @@ int __ref arch_remove_memory(u64 start, u64 size, int flags) zone = page_zone(page); ret = __remove_pages(zone, start_pfn, nr_pages); WARN_ON_ONCE(ret); - kernel_physical_mapping_remove(start, start + size); + + if (!(flags & MEMORY_UNADDRESSABLE)) + kernel_physical_mapping_remove(start, start + size); return ret; } -- 2.4.3