From: Dan Williams <dan.j.williams@intel.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>,
Christoph Hellwig <hch@lst.de>, Ben Skeggs <bskeggs@redhat.com>,
Felix Kuehling <Felix.Kuehling@amd.com>,
Ralph Campbell <rcampbell@nvidia.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 04/15] mm: remove the pgmap field from struct hmm_vma_walk
Date: Thu, 15 Aug 2019 12:36:58 -0700 [thread overview]
Message-ID: <CAPcyv4g4hzcEA=TPYVTiqpbtOoS30ahogRUttCvQAvXQbQjfnw@mail.gmail.com> (raw)
In-Reply-To: <20190815180325.GA4920@redhat.com>
On Thu, Aug 15, 2019 at 11:07 AM Jerome Glisse <jglisse@redhat.com> wrote:
>
> On Wed, Aug 14, 2019 at 07:48:28AM -0700, Dan Williams wrote:
> > On Wed, Aug 14, 2019 at 6:28 AM Jason Gunthorpe <jgg@mellanox.com> wrote:
> > >
> > > On Wed, Aug 14, 2019 at 09:38:54AM +0200, Christoph Hellwig wrote:
> > > > On Tue, Aug 13, 2019 at 06:36:33PM -0700, Dan Williams wrote:
> > > > > Section alignment constraints somewhat save us here. The only example
> > > > > I can think of a PMD not containing a uniform pgmap association for
> > > > > each pte is the case when the pgmap overlaps normal dram, i.e. shares
> > > > > the same 'struct memory_section' for a given span. Otherwise, distinct
> > > > > pgmaps arrange to manage their own exclusive sections (and now
> > > > > subsections as of v5.3). Otherwise the implementation could not
> > > > > guarantee different mapping lifetimes.
> > > > >
> > > > > That said, this seems to want a better mechanism to determine "pfn is
> > > > > ZONE_DEVICE".
> > > >
> > > > So I guess this patch is fine for now, and once you provide a better
> > > > mechanism we can switch over to it?
> > >
> > > What about the version I sent to just get rid of all the strange
> > > put_dev_pagemaps while scanning? Odds are good we will work with only
> > > a single pagemap, so it makes some sense to cache it once we find it?
> >
> > Yes, if the scan is over a single pmd then caching it makes sense.
>
> Quite frankly an easier an better solution is to remove the pagemap
> lookup as HMM user abide by mmu notifier it means we will not make
> use or dereference the struct page so that we are safe from any
> racing hotunplug of dax memory (as long as device driver using hmm
> do not have a bug).
Yes, as long as the driver remove is synchronized against HMM
operations via another mechanism then there is no need to take pagemap
references. Can you briefly describe what that other mechanism is?
next prev parent reply other threads:[~2019-08-15 19:37 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 16:05 hmm cleanups, v2 Christoph Hellwig
2019-08-06 16:05 ` [PATCH 01/15] amdgpu: remove -EAGAIN handling for hmm_range_fault Christoph Hellwig
2019-08-06 16:05 ` [PATCH 02/15] amdgpu: don't initialize range->list in amdgpu_hmm_init_range Christoph Hellwig
2019-08-06 16:05 ` [PATCH 03/15] nouveau: pass struct nouveau_svmm to nouveau_range_fault Christoph Hellwig
2019-08-06 18:02 ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 04/15] mm: remove the pgmap field from struct hmm_vma_walk Christoph Hellwig
2019-08-07 17:45 ` Jason Gunthorpe
2019-08-07 18:47 ` Dan Williams
2019-08-08 6:59 ` Christoph Hellwig
2019-08-14 1:36 ` Dan Williams
2019-08-14 7:38 ` Christoph Hellwig
2019-08-14 13:27 ` Jason Gunthorpe
2019-08-14 14:48 ` Dan Williams
2019-08-15 18:03 ` Jerome Glisse
2019-08-15 19:22 ` Jason Gunthorpe
2019-08-15 19:36 ` Dan Williams [this message]
2019-08-15 19:43 ` Jerome Glisse
2019-08-15 20:12 ` Dan Williams
2019-08-15 20:33 ` Jerome Glisse
2019-08-15 20:41 ` Jason Gunthorpe
2019-08-15 20:47 ` Dan Williams
2019-08-16 0:40 ` Jason Gunthorpe
2019-08-16 3:54 ` Dan Williams
2019-08-16 12:24 ` Jason Gunthorpe
2019-08-16 17:21 ` Dan Williams
2019-08-16 17:28 ` Jason Gunthorpe
2019-08-16 21:10 ` Ralph Campbell
2019-08-15 20:51 ` Jerome Glisse
2019-08-16 0:43 ` Jason Gunthorpe
2019-08-16 4:44 ` Christoph Hellwig
2019-08-16 12:30 ` Jason Gunthorpe
2019-08-16 12:34 ` Christoph Hellwig
2019-08-16 4:41 ` Christoph Hellwig
2019-08-06 16:05 ` [PATCH 05/15] mm: remove the unused vma argument to hmm_range_dma_unmap Christoph Hellwig
2019-08-06 16:05 ` [PATCH 06/15] mm: remove superflous arguments from hmm_range_register Christoph Hellwig
2019-08-06 16:05 ` [PATCH 07/15] mm: remove the page_shift member from struct hmm_range Christoph Hellwig
2019-08-07 17:51 ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 08/15] mm: remove the mask variable in hmm_vma_walk_hugetlb_entry Christoph Hellwig
2019-08-06 18:02 ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 09/15] mm: don't abuse pte_index() in hmm_vma_handle_pmd Christoph Hellwig
2019-08-07 17:18 ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 10/15] mm: only define hmm_vma_walk_pud if needed Christoph Hellwig
2019-08-06 16:05 ` [PATCH 11/15] mm: cleanup the hmm_vma_handle_pmd stub Christoph Hellwig
2019-08-06 18:00 ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 12/15] mm: cleanup the hmm_vma_walk_hugetlb_entry stub Christoph Hellwig
2019-08-06 16:05 ` [PATCH 13/15] mm: allow HMM_MIRROR on all architectures with MMU Christoph Hellwig
2019-08-06 16:05 ` [PATCH 14/15] mm: make HMM_MIRROR an implicit option Christoph Hellwig
2019-08-06 17:44 ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 15/15] amdgpu: remove CONFIG_DRM_AMDGPU_USERPTR Christoph Hellwig
2019-08-06 17:44 ` Jason Gunthorpe
2019-08-06 17:51 ` Kuehling, Felix
2019-08-06 18:58 ` Alex Deucher
2019-08-06 20:03 ` Jason Gunthorpe
2019-08-07 6:57 ` Koenig, Christian
2019-08-07 11:46 ` Jason Gunthorpe
2019-08-07 18:17 ` hmm cleanups, v2 Jason Gunthorpe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAPcyv4g4hzcEA=TPYVTiqpbtOoS30ahogRUttCvQAvXQbQjfnw@mail.gmail.com' \
--to=dan.j.williams@intel.com \
--cc=Felix.Kuehling@amd.com \
--cc=amd-gfx@lists.freedesktop.org \
--cc=bskeggs@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@lst.de \
--cc=jgg@mellanox.com \
--cc=jglisse@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=nouveau@lists.freedesktop.org \
--cc=rcampbell@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).