From: Mark Hairgrove <mhairgrove@nvidia.com>
To: Jerome Glisse <j.glisse@gmail.com>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
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"Duncan Poole" <dpoole@nvidia.com>,
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"John Hubbard" <jhubbard@nvidia.com>,
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"Arvind Gopalakrishnan" <arvindg@nvidia.com>,
"Haggai Eran" <haggaie@mellanox.com>,
"Shachar Raindel" <raindel@mellanox.com>,
"Liran Liss" <liranl@mellanox.com>,
"Roland Dreier" <roland@purestorage.com>,
"Ben Sander" <ben.sander@amd.com>,
"Greg Stoner" <Greg.Stoner@amd.com>,
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"Michael Mantor" <Michael.Mantor@amd.com>,
"Paul Blinzer" <Paul.Blinzer@amd.com>,
"Laurent Morichetti" <Laurent.Morichetti@amd.com>,
"Alexander Deucher" <Alexander.Deucher@amd.com>,
"Oded Gabbay" <Oded.Gabbay@amd.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jatin Kumar" <jakumar@nvidia.com>
Subject: Re: [PATCH 07/36] HMM: add per mirror page table v3.
Date: Fri, 26 Jun 2015 20:02:03 -0700 [thread overview]
Message-ID: <alpine.DEB.2.00.1506261958010.22464@mdh-linux64-2.nvidia.com> (raw)
In-Reply-To: <20150626164338.GB3748@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 4218 bytes --]
On Fri, 26 Jun 2015, Jerome Glisse wrote:
> On Thu, Jun 25, 2015 at 04:05:48PM -0700, Mark Hairgrove wrote:
> > On Thu, 21 May 2015, j.glisse@gmail.com wrote:
> > > From: Jerome Glisse <jglisse@redhat.com>
> > > [...]
> > >
> > > + /* update() - update device mmu following an event.
> > > + *
> > > + * @mirror: The mirror that link process address space with the device.
> > > + * @event: The event that triggered the update.
> > > + * Returns: 0 on success or error code {-EIO, -ENOMEM}.
> > > + *
> > > + * Called to update device page table for a range of address.
> > > + * The event type provide the nature of the update :
> > > + * - Range is no longer valid (munmap).
> > > + * - Range protection changes (mprotect, COW, ...).
> > > + * - Range is unmapped (swap, reclaim, page migration, ...).
> > > + * - Device page fault.
> > > + * - ...
> > > + *
> > > + * Thought most device driver only need to use pte_mask as it reflects
> > > + * change that will happen to the HMM page table ie :
> > > + * new_pte = old_pte & event->pte_mask;
> >
> > Documentation request: It would be useful to break down exactly what is
> > required from the driver for each event type here, and what extra
> > information is provided by the type that isn't provided by the pte_mask.
>
> Mostly event tell you if you need to free or not the device page table for
> the range, which is not something you can infer from the pte_mask reliably.
> Difference btw migration and munmap for instance, same pte_mask but range
> is still valid in the migration case it will just be backed by a new set of
> pages.
Given that event->pte_mask and event->type provide redundant information,
are they both necessary?
With or without pte_mask, the below table would be helpful to have in the
comments for the ->update callback:
Event type Driver action
HMM_NONE N/A (driver will never get this)
HMM_FORK Same as HMM_WRITE_PROTECT
HMM_ISDIRTY Same as HMM_WRITE_PROTECT
HMM_MIGRATE Make device PTEs invalid and use hmm_pte_set_dirty or
hmm_mirror_range_dirty if applicable
HMM_MUNMAP Same as HMM_MIGRATE, but the driver may take this as a
hint to free device page tables and other resources
associated with this range
HMM_DEVICE_RFAULT Read hmm_ptes using hmm_pt_iter and write them on the
device
HMM_DEVICE_WFAULT Same as HMM_DEVICE_RFAULT
HMM_WRITE_PROTECT Remove write permission from device PTEs and use
hmm_pte_set_dirty or hmm_mirror_range_dirty if
applicable
>
>
> [...]
> > > @@ -142,6 +223,7 @@ int hmm_device_unregister(struct hmm_device *device);
> > > * @kref: Reference counter (private to HMM do not use).
> > > * @dlist: List of all hmm_mirror for same device.
> > > * @mlist: List of all hmm_mirror for same process.
> > > + * @pt: Mirror page table.
> > > *
> > > * Each device that want to mirror an address space must register one of this
> > > * struct for each of the address space it wants to mirror. Same device can
> > > @@ -154,6 +236,7 @@ struct hmm_mirror {
> > > struct kref kref;
> > > struct list_head dlist;
> > > struct hlist_node mlist;
> > > + struct hmm_pt pt;
> >
> > Documentation request: Why does each mirror have its own separate set of
> > page tables rather than the hmm keeping one set for all devices? This is
> > so different devices can have different permissions for the same address
> > range, correct?
>
> Several reasons, first and mostly dma mapping, while i have plan to allow
> to share dma mapping directory btw devices this require work in the dma
> layer first. Second reasons is, like you point out, different permissions,
> like one device requesting atomic access ie the device will be the only
> one with write permission and HMM need somewhere to store that information
> per device per address. It also helps to avoid calling device driver on a
> range that one device does not mirror.
Sure, that makes sense. Can you put this in the documentation somewhere,
perhaps in the header comments for struct hmm_mirror?
Thanks!
next prev parent reply other threads:[~2015-06-27 3:02 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-21 19:31 HMM (Heterogeneous Memory Management) v8 j.glisse
2015-05-21 19:31 ` [PATCH 01/36] mmu_notifier: add event information to address invalidation v7 j.glisse
2015-05-30 3:43 ` John Hubbard
2015-06-01 19:03 ` Jerome Glisse
2015-06-01 23:10 ` John Hubbard
2015-06-03 16:07 ` Jerome Glisse
2015-06-03 23:02 ` John Hubbard
2015-05-21 19:31 ` [PATCH 02/36] mmu_notifier: keep track of active invalidation ranges v3 j.glisse
2015-05-27 5:09 ` Aneesh Kumar K.V
2015-05-27 14:32 ` Jerome Glisse
2015-06-02 9:32 ` John Hubbard
2015-06-03 17:15 ` Jerome Glisse
2015-06-05 3:29 ` John Hubbard
2015-05-21 19:31 ` [PATCH 03/36] mmu_notifier: pass page pointer to mmu_notifier_invalidate_page() j.glisse
2015-05-27 5:17 ` Aneesh Kumar K.V
2015-05-27 14:33 ` Jerome Glisse
2015-06-03 4:25 ` John Hubbard
2015-05-21 19:31 ` [PATCH 04/36] mmu_notifier: allow range invalidation to exclude a specific mmu_notifier j.glisse
2015-05-21 19:31 ` [PATCH 05/36] HMM: introduce heterogeneous memory management v3 j.glisse
2015-05-27 5:50 ` Aneesh Kumar K.V
2015-05-27 14:38 ` Jerome Glisse
2015-06-08 19:40 ` Mark Hairgrove
2015-06-08 21:17 ` Jerome Glisse
2015-06-09 1:54 ` Mark Hairgrove
2015-06-09 15:56 ` Jerome Glisse
2015-06-10 3:33 ` Mark Hairgrove
2015-06-10 15:42 ` Jerome Glisse
2015-06-11 1:15 ` Mark Hairgrove
2015-06-11 14:23 ` Jerome Glisse
2015-06-11 22:26 ` Mark Hairgrove
2015-06-15 14:32 ` Jerome Glisse
2015-05-21 19:31 ` [PATCH 06/36] HMM: add HMM page table v2 j.glisse
2015-06-19 2:06 ` Mark Hairgrove
2015-06-19 18:07 ` Jerome Glisse
2015-06-20 2:34 ` Mark Hairgrove
2015-06-25 22:57 ` Mark Hairgrove
2015-06-26 16:30 ` Jerome Glisse
2015-06-27 1:34 ` Mark Hairgrove
2015-06-29 14:43 ` Jerome Glisse
2015-07-01 2:51 ` Mark Hairgrove
2015-07-01 15:07 ` Jerome Glisse
2015-05-21 19:31 ` [PATCH 07/36] HMM: add per mirror page table v3 j.glisse
2015-06-25 23:05 ` Mark Hairgrove
2015-06-26 16:43 ` Jerome Glisse
2015-06-27 3:02 ` Mark Hairgrove [this message]
2015-06-29 14:50 ` Jerome Glisse
2015-05-21 19:31 ` [PATCH 08/36] HMM: add device page fault support v3 j.glisse
2015-05-21 19:31 ` [PATCH 09/36] HMM: add mm page table iterator helpers j.glisse
2015-05-21 19:31 ` [PATCH 10/36] HMM: use CPU page table during invalidation j.glisse
2015-05-21 19:31 ` [PATCH 11/36] HMM: add discard range helper (to clear and free resources for a range) j.glisse
2015-05-21 19:31 ` [PATCH 12/36] HMM: add dirty range helper (to toggle dirty bit inside mirror page table) j.glisse
2015-05-21 19:31 ` [PATCH 13/36] HMM: DMA map memory on behalf of device driver j.glisse
2015-05-21 19:31 ` [PATCH 14/36] fork: pass the dst vma to copy_page_range() and its sub-functions j.glisse
2015-05-21 19:31 ` [PATCH 15/36] memcg: export get_mem_cgroup_from_mm() j.glisse
2015-05-21 19:31 ` [PATCH 16/36] HMM: add special swap filetype for memory migrated to HMM device memory j.glisse
2015-06-24 7:49 ` Haggai Eran
2015-05-21 19:31 ` [PATCH 17/36] HMM: add new HMM page table flag (valid device memory) j.glisse
2015-05-21 19:31 ` [PATCH 18/36] HMM: add new HMM page table flag (select flag) j.glisse
2015-05-21 19:31 ` [PATCH 19/36] HMM: handle HMM device page table entry on mirror page table fault and update j.glisse
2015-05-21 20:22 ` [PATCH 20/36] HMM: mm add helper to update page table when migrating memory back jglisse
2015-05-21 20:22 ` [PATCH 21/36] HMM: mm add helper to update page table when migrating memory jglisse
2015-05-21 20:22 ` [PATCH 22/36] HMM: add new callback for copying memory from and to device memory jglisse
2015-05-21 20:22 ` [PATCH 23/36] HMM: allow to get pointer to spinlock protecting a directory jglisse
2015-05-21 20:23 ` [PATCH 24/36] HMM: split DMA mapping function in two jglisse
2015-05-21 20:23 ` [PATCH 25/36] HMM: add helpers for migration back to system memory jglisse
2015-05-21 20:23 ` [PATCH 26/36] HMM: fork copy migrated memory into system memory for child process jglisse
2015-05-21 20:23 ` [PATCH 27/36] HMM: CPU page fault on migrated memory jglisse
2015-05-21 20:23 ` [PATCH 28/36] HMM: add mirror fault support for system to device memory migration jglisse
2015-05-21 20:23 ` [PATCH 29/36] IB/mlx5: add a new paramter to __mlx_ib_populated_pas for ODP with HMM jglisse
2015-05-21 20:23 ` [PATCH 30/36] IB/mlx5: add a new paramter to mlx5_ib_update_mtt() " jglisse
2015-05-21 20:23 ` [PATCH 31/36] IB/odp: export rbt_ib_umem_for_each_in_range() jglisse
2015-05-21 20:23 ` [PATCH 32/36] IB/odp/hmm: add new kernel option to use HMM for ODP jglisse
2015-05-21 20:23 ` [PATCH 33/36] IB/odp/hmm: add core infiniband structure and helper for ODP with HMM jglisse
2015-06-24 13:59 ` Haggai Eran
2015-05-21 20:23 ` [PATCH 34/36] IB/mlx5/hmm: add mlx5 HMM device initialization and callback jglisse
2015-05-21 20:23 ` [PATCH 35/36] IB/mlx5/hmm: add page fault support for ODP on HMM jglisse
2015-05-21 20:23 ` [PATCH 36/36] IB/mlx5/hmm: enable ODP using HMM jglisse
2015-05-30 3:01 ` HMM (Heterogeneous Memory Management) v8 John Hubbard
2015-05-31 6:56 ` Haggai Eran
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