From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-f200.google.com (mail-yw0-f200.google.com [209.85.161.200]) by kanga.kvack.org (Postfix) with ESMTP id CD9C4440846 for ; Tue, 11 Jul 2017 03:31:23 -0400 (EDT) Received: by mail-yw0-f200.google.com with SMTP id g195so107629682ywe.10 for ; Tue, 11 Jul 2017 00:31:23 -0700 (PDT) Received: from mail-yb0-x22a.google.com (mail-yb0-x22a.google.com. [2607:f8b0:4002:c09::22a]) by mx.google.com with ESMTPS id j190si3703719ywd.474.2017.07.11.00.31.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Jul 2017 00:31:22 -0700 (PDT) Received: by mail-yb0-x22a.google.com with SMTP id f194so35271814yba.3 for ; Tue, 11 Jul 2017 00:31:22 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170705184933.GD3305@redhat.com> References: <20170703211415.11283-1-jglisse@redhat.com> <20170703211415.11283-2-jglisse@redhat.com> <20170705142516.GA3305@redhat.com> <20170705184933.GD3305@redhat.com> From: Dan Williams Date: Tue, 11 Jul 2017 00:31:22 -0700 Message-ID: Subject: Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory_type one Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Glisse Cc: "linux-kernel@vger.kernel.org" , Linux MM , John Hubbard , David Nellans , Balbir Singh , Ross Zwisler On Wed, Jul 5, 2017 at 11:49 AM, Jerome Glisse wrote: > On Wed, Jul 05, 2017 at 09:15:35AM -0700, Dan Williams wrote: >> 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, J=C3=A9r=C3=B4me Glisse wrote: >> >> > Use consistent name between IORES_DESC and enum memory_type, rename >> >> > MEMORY_DEVICE_PUBLIC to MEMORY_DEVICE_PERSISTENT. This is to free u= p >> >> > the public name for CDM (cache coherent device memory) for which th= e >> >> > term public is a better match. >> >> > >> >> > Signed-off-by: J=C3=A9r=C3=B4me 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 d= ifferents >> >> > * 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 =3D 0, >> >> > + MEMORY_DEVICE_PERSISTENT =3D 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, s= truct resource *res, >> >> > } >> >> > pgmap->ref =3D ref; >> >> > pgmap->res =3D &page_map->res; >> >> > - pgmap->type =3D MEMORY_DEVICE_PUBLIC; >> >> > + pgmap->type =3D MEMORY_DEVICE_PERSISTENT; >> >> > pgmap->page_fault =3D NULL; >> >> > pgmap->page_free =3D NULL; >> >> > pgmap->data =3D 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 onl= y >> >> 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. > > I want to distinguish between: > - device memory that is not accessible by the CPU > - device memory that is accessible by the CPU just like regular > memory > - existing user of devm_memremap_pages() which is persistent memory > (only pmem seems to call devm_memremap_pages()) that is use like a > filesystem or block device and thus isn't use like generic page in > a process address space > > So if existing user of devm_memremap_pages() are only persistent memory > then it made sense to match the IORES_DESC we are expecting to see on > see such memory. > > For public device memory (in the sense introduced by this patchset) i > do not know how it will be described by IORES_DESC. i think first folks > with it are IBM with CAPI and i am not sure they defined something for > that already. > > I am open to any name beside public (well any reasonable name :)) but > i do need to be able to distinguish persistent memory as use today from > this device memory. Right, so that's why I suggested MEMORY_DEVICE_HOST for memory that is just normal host memory and does not have any device-entanglements outside of the base ZONE_DEVICE registration. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org