Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760329AbcCECXe (ORCPT ); Fri, 4 Mar 2016 21:23:34 -0500 Received: from mail-qg0-f67.google.com ([209.85.192.67]:36500 "EHLO mail-qg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759462AbcCECXc (ORCPT ); Fri, 4 Mar 2016 21:23:32 -0500 MIME-Version: 1.0 In-Reply-To: <1457146138.15454.277.camel@hpe.com> References: <20160303215304.1014.69931.stgit@dwillia2-desk3.amr.corp.intel.com> <20160303215315.1014.95661.stgit@dwillia2-desk3.amr.corp.intel.com> <1457146138.15454.277.camel@hpe.com> Date: Fri, 4 Mar 2016 18:23:31 -0800 X-Google-Sender-Auth: iRf0u4BbSxAUQbG9uTzW_hG_Rmg Message-ID: Subject: Re: [PATCH v2 2/3] libnvdimm, pmem: adjust for section collisions with 'System RAM' From: Dan Williams To: Toshi Kani Cc: "linux-nvdimm@lists.01.org" , linux-mm , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3702 Lines: 93 On Fri, Mar 4, 2016 at 6:48 PM, Toshi Kani wrote: > On Thu, 2016-03-03 at 13:53 -0800, Dan Williams wrote: >> On a platform where 'Persistent Memory' and 'System RAM' are mixed >> within a given sparsemem section, trim the namespace and notify about the >> sub-optimal alignment. >> >> Cc: Toshi Kani >> Cc: Ross Zwisler >> Signed-off-by: Dan Williams >> --- >> drivers/nvdimm/namespace_devs.c | 7 ++ >> drivers/nvdimm/pfn.h | 10 ++- >> drivers/nvdimm/pfn_devs.c | 5 ++ >> drivers/nvdimm/pmem.c | 125 ++++++++++++++++++++++++++++----- >> ------ >> 4 files changed, 111 insertions(+), 36 deletions(-) >> >> diff --git a/drivers/nvdimm/namespace_devs.c >> b/drivers/nvdimm/namespace_devs.c >> index 8ebfcaae3f5a..463756ca2d4b 100644 >> --- a/drivers/nvdimm/namespace_devs.c >> +++ b/drivers/nvdimm/namespace_devs.c >> @@ -133,6 +133,7 @@ bool nd_is_uuid_unique(struct device *dev, u8 *uuid) >> bool pmem_should_map_pages(struct device *dev) >> { >> struct nd_region *nd_region = to_nd_region(dev->parent); >> + struct nd_namespace_io *nsio; >> >> if (!IS_ENABLED(CONFIG_ZONE_DEVICE)) >> return false; >> @@ -143,6 +144,12 @@ bool pmem_should_map_pages(struct device *dev) >> if (is_nd_pfn(dev) || is_nd_btt(dev)) >> return false; >> >> + nsio = to_nd_namespace_io(dev); >> + if (region_intersects(nsio->res.start, resource_size(&nsio- >> >res), >> + IORESOURCE_SYSTEM_RAM, >> + IORES_DESC_NONE) == REGION_MIXED) > > Should this be != REGION_DISJOINT for safe? Acutally, it's ok. It doesn't need to be disjoint. The problem is mixing an mm-zone within a given section. If the region intersects system-ram then devm_memremap_pages() is a no-op and we can use the existing page allocation and linear mapping. > >> + return false; >> + > > : > >> @@ -304,21 +311,56 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) >> } >> >> memset(pfn_sb, 0, sizeof(*pfn_sb)); >> - npfns = (pmem->size - SZ_8K) / SZ_4K; >> + >> + /* >> + * Check if pmem collides with 'System RAM' when section aligned >> and >> + * trim it accordingly >> + */ >> + nsio = to_nd_namespace_io(&ndns->dev); >> + start = PHYS_SECTION_ALIGN_DOWN(nsio->res.start); >> + size = resource_size(&nsio->res); >> + if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM, >> + IORES_DESC_NONE) == REGION_MIXED) { >> + >> + start = nsio->res.start; >> + start_pad = PHYS_SECTION_ALIGN_UP(start) - start; >> + } >> + >> + start = nsio->res.start; >> + size = PHYS_SECTION_ALIGN_UP(start + size) - start; >> + if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM, >> + IORES_DESC_NONE) == REGION_MIXED) { >> + size = resource_size(&nsio->res); >> + end_trunc = start + size - PHYS_SECTION_ALIGN_DOWN(start >> + size); >> + } > > This check seems to assume that guest's regular memory layout does not > change. That is, if there is no collision at first, there won't be any > later. Is this a valid assumption? If platform firmware changes the physical alignment during the lifetime of the namespace there's not much we can do. Another problem not addressed by this patch is firmware choosing to hot plug system ram into the same section as persistent memory. As far as I can see all we do is ask firmware implementations to respect Linux section boundaries and otherwise not change alignments.