From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id D3A056B04B3 for ; Mon, 10 Jul 2017 23:48:37 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id e3so133237392pfc.4 for ; Mon, 10 Jul 2017 20:48:37 -0700 (PDT) Received: from mail-pf0-x241.google.com (mail-pf0-x241.google.com. [2607:f8b0:400e:c00::241]) by mx.google.com with ESMTPS id v66si9117613pfb.416.2017.07.10.20.48.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Jul 2017 20:48:36 -0700 (PDT) Received: by mail-pf0-x241.google.com with SMTP id z6so17098161pfk.3 for ; Mon, 10 Jul 2017 20:48:36 -0700 (PDT) Date: Tue, 11 Jul 2017 13:48:21 +1000 From: Balbir Singh Subject: Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory_type one Message-ID: <20170711134821.433b88c1@firefly.ozlabs.ibm.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Glisse Cc: Dan Williams , "linux-kernel@vger.kernel.org" , Linux MM , John Hubbard , David Nellans , Ross Zwisler On Wed, 5 Jul 2017 14:49:33 -0400 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 wrot= e: =20 > > > On Mon, Jul 03, 2017 at 04:49:18PM -0700, Dan Williams wrote: =20 > > >> On Mon, Jul 3, 2017 at 2:14 PM, J=C3=A9r=C3=B4me Glisse wrote: =20 > > >> > 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 t= he > > >> > 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 = differents > > >> > * usage. > > >> > * > > >> > - * MEMORY_DEVICE_PUBLIC: > > >> > + * MEMORY_DEVICE_PERSISTENT: > > >> > * Persistent device memory (pmem): struct page might be allocate= d 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, = struct 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; =20 > > >> > > >> 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 on= ly > > >> 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 */ =20 > > > > > > No that would not work. Device public (in the context of this patchse= t) > > > 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. > > > =20 > >=20 > > 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. =20 >=20 > 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 >=20 > 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. >=20 > 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. >=20 > 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. >=20 > Cheers, > J=C3=A9r=C3=B4me -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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