From: Christoph Hellwig <hch@lst.de>
To: Felix Kuehling <felix.kuehling@amd.com>
Cc: Christoph Hellwig <hch@lst.de>, Alex Sierra <alex.sierra@amd.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
rcampbell@nvidia.com, linux-ext4@vger.kernel.org,
linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, jgg@nvidia.com,
jglisse@redhat.com, Roger Pau Monne <roger.pau@citrix.com>,
Dan Williams <dan.j.williams@intel.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v6 08/13] mm: call pgmap->ops->page_free for DEVICE_GENERIC pages
Date: Fri, 20 Aug 2021 07:05:04 +0200 [thread overview]
Message-ID: <20210820050504.GB27083@lst.de> (raw)
In-Reply-To: <e5eb53f9-c52a-52e1-5fa0-bb468c0c9c85@amd.com>
On Tue, Aug 17, 2021 at 11:44:54AM -0400, Felix Kuehling wrote:
> >> That's a good catch. Existing drivers shouldn't need a page_free
> >> callback if they didn't have one before. That means we need to add a
> >> NULL-pointer check in free_device_page.
> > Also the other state clearing (__ClearPageWaiters/mem_cgroup_uncharge/
> > ->mapping = NULL).
> >
> > In many ways this seems like you want to bring back the DEVICE_PUBLIC
> > pgmap type that was removed a while ago due to the lack of users
> > instead of overloading the generic type.
>
> I think so. I'm not clear about how DEVICE_PUBLIC differed from what
> DEVICE_GENERIC is today. As I understand it, DEVICE_PUBLIC was removed
> because it was unused and also known to be broken in some ways.
> DEVICE_GENERIC seemed close enough to what we need, other than not being
> supported in the migration helpers.
>
> Would you see benefit in re-introducing DEVICE_PUBLIC as a distinct
> memory type from DEVICE_GENERIC? What would be the benefits of making
> that distinction?
The old DEVICE_PUBLIC mostly different in that it allowed the page
to be returned from vm_normal_page, which I think was horribly buggy.
But the point is not to bring back these old semantics. The idea
is to be able to differeniate between your new coherent on-device
memory and the existing DEVICE_GENERIC. That is call the
code in free_devmap_managed_page that is currently only used
for device private pages also for your new public device pages without
affecting the devdax and xen use cases.
next prev parent reply other threads:[~2021-08-20 5:05 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-13 6:31 [PATCH v6 00/13] Support DEVICE_GENERIC memory in migrate_vma_* Alex Sierra
2021-08-13 6:31 ` [PATCH v6 01/13] ext4/xfs: add page refcount helper Alex Sierra
2021-08-15 9:01 ` Christoph Hellwig
2021-08-13 6:31 ` [PATCH v6 02/13] mm: remove extra ZONE_DEVICE struct page refcount Alex Sierra
2021-08-15 15:37 ` Christoph Hellwig
2021-08-15 20:40 ` John Hubbard
2021-08-16 18:56 ` Felix Kuehling
2021-08-20 6:33 ` Jerome Glisse
2021-08-18 0:01 ` Ralph Campbell
2021-08-18 0:35 ` Felix Kuehling
2021-08-18 19:28 ` Ralph Campbell
2021-08-19 18:00 ` Sierra Guiza, Alejandro (Alex)
2021-08-19 19:59 ` Felix Kuehling
2021-08-20 4:40 ` Christoph Hellwig
2021-08-20 7:17 ` Jerome Glisse
2021-08-20 4:56 ` Christoph Hellwig
2021-08-13 6:31 ` [PATCH v6 03/13] kernel: resource: lookup_resource as exported symbol Alex Sierra
2021-08-13 6:31 ` [PATCH v6 04/13] drm/amdkfd: add SPM support for SVM Alex Sierra
2021-08-15 9:10 ` Christoph Hellwig
2021-08-16 18:54 ` Felix Kuehling
2021-08-17 5:47 ` Christoph Hellwig
2021-08-13 6:31 ` [PATCH v6 05/13] drm/amdkfd: generic type as sys mem on migration to ram Alex Sierra
2021-08-15 15:38 ` Christoph Hellwig
2021-08-16 19:53 ` Sierra Guiza, Alejandro (Alex)
2021-08-16 22:06 ` Zeng, Oak
2021-08-17 0:42 ` Felix Kuehling
2021-08-17 5:49 ` Christoph Hellwig
2021-08-13 6:31 ` [PATCH v6 06/13] include/linux/mm.h: helpers to check zone device generic type Alex Sierra
2021-08-15 9:16 ` Christoph Hellwig
2021-08-13 6:31 ` [PATCH v6 07/13] mm: add generic type support to migrate_vma helpers Alex Sierra
2021-08-15 9:19 ` Christoph Hellwig
2021-08-13 6:31 ` [PATCH v6 08/13] mm: call pgmap->ops->page_free for DEVICE_GENERIC pages Alex Sierra
2021-08-15 15:40 ` Christoph Hellwig
2021-08-16 19:00 ` Felix Kuehling
2021-08-17 5:50 ` Christoph Hellwig
2021-08-17 15:44 ` Felix Kuehling
2021-08-20 5:05 ` Christoph Hellwig [this message]
2021-08-20 7:24 ` Jerome Glisse
2021-08-13 6:31 ` [PATCH v6 09/13] lib: test_hmm add ioctl to get zone device type Alex Sierra
2021-08-13 6:31 ` [PATCH v6 10/13] lib: test_hmm add module param for " Alex Sierra
2021-08-13 6:31 ` [PATCH v6 11/13] lib: add support for device generic type in test_hmm Alex Sierra
2021-08-13 6:31 ` [PATCH v6 12/13] tools: update hmm-test to support device generic type Alex Sierra
2021-08-13 6:31 ` [PATCH v6 13/13] tools: update test_hmm script to support SP config Alex Sierra
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