From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751892AbdGEQPj (ORCPT ); Wed, 5 Jul 2017 12:15:39 -0400 Received: from mail-yb0-f169.google.com ([209.85.213.169]:34569 "EHLO mail-yb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678AbdGEQPi (ORCPT ); Wed, 5 Jul 2017 12:15:38 -0400 MIME-Version: 1.0 In-Reply-To: <20170705142516.GA3305@redhat.com> References: <20170703211415.11283-1-jglisse@redhat.com> <20170703211415.11283-2-jglisse@redhat.com> <20170705142516.GA3305@redhat.com> From: Dan Williams Date: Wed, 5 Jul 2017 09:15:35 -0700 Message-ID: Subject: Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory_type one To: Jerome Glisse Cc: "linux-kernel@vger.kernel.org" , Linux MM , John Hubbard , David Nellans , Balbir Singh , Ross Zwisler 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-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v65GFi7G029394 On Wed, Jul 5, 2017 at 7:25 AM, Jerome Glisse wrote: > On Mon, Jul 03, 2017 at 04:49:18PM -0700, Dan Williams wrote: >> On Mon, Jul 3, 2017 at 2:14 PM, Jérôme Glisse wrote: >> > Use consistent name between IORES_DESC and enum memory_type, rename >> > MEMORY_DEVICE_PUBLIC to MEMORY_DEVICE_PERSISTENT. This is to free up >> > the public name for CDM (cache coherent device memory) for which the >> > term public is a better match. >> > >> > Signed-off-by: Jérôme Glisse >> > Cc: Dan Williams >> > Cc: Ross Zwisler >> > --- >> > include/linux/memremap.h | 4 ++-- >> > kernel/memremap.c | 2 +- >> > 2 files changed, 3 insertions(+), 3 deletions(-) >> > >> > diff --git a/include/linux/memremap.h b/include/linux/memremap.h >> > index 57546a07a558..2299cc2d387d 100644 >> > --- a/include/linux/memremap.h >> > +++ b/include/linux/memremap.h >> > @@ -41,7 +41,7 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) >> > * Specialize ZONE_DEVICE memory into multiple types each having differents >> > * usage. >> > * >> > - * MEMORY_DEVICE_PUBLIC: >> > + * MEMORY_DEVICE_PERSISTENT: >> > * Persistent device memory (pmem): struct page might be allocated in different >> > * memory and architecture might want to perform special actions. It is similar >> > * to regular memory, in that the CPU can access it transparently. However, >> > @@ -59,7 +59,7 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) >> > * include/linux/hmm.h and Documentation/vm/hmm.txt. >> > */ >> > enum memory_type { >> > - MEMORY_DEVICE_PUBLIC = 0, >> > + MEMORY_DEVICE_PERSISTENT = 0, >> > MEMORY_DEVICE_PRIVATE, >> > }; >> > >> > diff --git a/kernel/memremap.c b/kernel/memremap.c >> > index b9baa6c07918..e82456c39a6a 100644 >> > --- a/kernel/memremap.c >> > +++ b/kernel/memremap.c >> > @@ -350,7 +350,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, >> > } >> > pgmap->ref = ref; >> > pgmap->res = &page_map->res; >> > - pgmap->type = MEMORY_DEVICE_PUBLIC; >> > + pgmap->type = MEMORY_DEVICE_PERSISTENT; >> > pgmap->page_fault = NULL; >> > pgmap->page_free = NULL; >> > pgmap->data = NULL; >> >> I think we need a different name. There's nothing "persistent" about >> the devm_memremap_pages() path. Why can't they share name, is the only >> difference coherence? I'm thinking something like: >> >> MEMORY_DEVICE_PRIVATE >> MEMORY_DEVICE_COHERENT /* persistent memory and coherent devices */ >> MEMORY_DEVICE_IO /* "public", but not coherent */ > > No that would not work. Device public (in the context of this patchset) > is like device private ie device public page can be anywhere inside a > process address space either as anonymous memory page or as file back > page of regular filesystem (ie vma->ops is not pointing to anything > specific to the device memory). > > As such device public is different from how persistent memory is use > and those the cache coherency being the same between the two kind of > memory is not a discerning factor. So i need to distinguish between > persistent memory and device public memory. > > I believe keeping enum memory_type close to IORES_DESC naming is the > cleanest way to do that but i am open to other name suggestion. > The IORES_DESC has nothing to do with how the memory range is handled by the core mm. It sounds like the distinction this is trying to make is between MEMORY_DEVICE_{PUBLIC,PRIVATE} and MEMORY_DEVICE_HOST. Where a "host" memory range is one that does not need coordination with a specific device.