mbox series

[v6,0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables

Message ID 20181210011504.122604-1-drinkcat@chromium.org (mailing list archive)
Headers show
Series iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables | expand

Message

Nicolas Boichat Dec. 10, 2018, 1:15 a.m. UTC
This is a follow-up to the discussion in [1], [2].

IOMMUs using ARMv7 short-descriptor format require page tables
(level 1 and 2) to be allocated within the first 4GB of RAM, even
on 64-bit systems.

For L1 tables that are bigger than a page, we can just use __get_free_pages
with GFP_DMA32 (on arm64 systems only, arm would still use GFP_DMA).

For L2 tables that only take 1KB, it would be a waste to allocate a full
page, so we considered 3 approaches:
 1. This series, adding support for GFP_DMA32 slab caches.
 2. genalloc, which requires pre-allocating the maximum number of L2 page
    tables (4096, so 4MB of memory).
 3. page_frag, which is not very memory-efficient as it is unable to reuse
    freed fragments until the whole page is freed. [3]

This series is the most memory-efficient approach.

stable@ note:
  We confirmed that this is a regression, and IOMMU errors happen on 4.19
  and linux-next/master on MT8173 (elm, Acer Chromebook R13). The issue
  most likely starts from commit ad67f5a6545f ("arm64: replace ZONE_DMA
  with ZONE_DMA32"), i.e. 4.15, and presumably breaks a number of Mediatek
  platforms (and maybe others?).

[1] https://lists.linuxfoundation.org/pipermail/iommu/2018-November/030876.html
[2] https://lists.linuxfoundation.org/pipermail/iommu/2018-December/031696.html
[3] https://patchwork.codeaurora.org/patch/671639/

Changes since v1:
 - Add support for SLAB_CACHE_DMA32 in slab and slub (patches 1/2)
 - iommu/io-pgtable-arm-v7s (patch 3):
   - Changed approach to use SLAB_CACHE_DMA32 added by the previous
     commit.
   - Use DMA or DMA32 depending on the architecture (DMA for arm,
     DMA32 for arm64).

Changes since v2:
 - Reworded and expanded commit messages
 - Added cache_dma32 documentation in PATCH 2/3.

v3 used the page_frag approach, see [3].

Changes since v4:
 - Dropped change that removed GFP_DMA32 from GFP_SLAB_BUG_MASK:
   instead we can just call kmem_cache_*alloc without GFP_DMA32
   parameter. This also means that we can drop PATCH v4 1/3, as we
   do not make any changes in GFP flag verification.
 - Dropped hunks that added cache_dma32 sysfs file, and moved
   the hunks to PATCH v5 3/3, so that maintainer can decide whether
   to pick the change independently.

Changes since v5:
 - Rename ARM_V7S_TABLE_SLAB_CACHE to ARM_V7S_TABLE_SLAB_FLAGS.
 - Add stable@ to cc.

Nicolas Boichat (3):
  mm: Add support for kmem caches in DMA32 zone
  iommu/io-pgtable-arm-v7s: Request DMA32 memory, and improve debugging
  mm: Add /sys/kernel/slab/cache/cache_dma32

 Documentation/ABI/testing/sysfs-kernel-slab |  9 +++++++++
 drivers/iommu/io-pgtable-arm-v7s.c          | 19 +++++++++++++++----
 include/linux/slab.h                        |  2 ++
 mm/slab.c                                   |  2 ++
 mm/slab.h                                   |  3 ++-
 mm/slab_common.c                            |  2 +-
 mm/slub.c                                   | 16 ++++++++++++++++
 tools/vm/slabinfo.c                         |  7 ++++++-
 8 files changed, 53 insertions(+), 7 deletions(-)

Comments

Joerg Roedel Jan. 11, 2019, 10:21 a.m. UTC | #1
On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
> Does anyone have any further comment on this series? If not, which
> maintainer is going to pick this up? I assume Andrew Morton?

Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
this should go through mm.

Regards,

	Joerg
Nicolas Boichat Jan. 22, 2019, 10:51 p.m. UTC | #2
Hi Andrew,

On Fri, Jan 11, 2019 at 6:21 PM Joerg Roedel <joro@8bytes.org> wrote:
>
> On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
> > Does anyone have any further comment on this series? If not, which
> > maintainer is going to pick this up? I assume Andrew Morton?
>
> Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
> this should go through mm.

Gentle ping on this series, it seems like it's better if it goes
through your tree.

Series still applies cleanly on linux-next, but I'm happy to resend if
that helps.

Thanks!

> Regards,
>
>         Joerg
Vlastimil Babka Feb. 13, 2019, 5:12 p.m. UTC | #3
On 1/22/19 11:51 PM, Nicolas Boichat wrote:
> Hi Andrew,
> 
> On Fri, Jan 11, 2019 at 6:21 PM Joerg Roedel <joro@8bytes.org> wrote:
>>
>> On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
>> > Does anyone have any further comment on this series? If not, which
>> > maintainer is going to pick this up? I assume Andrew Morton?
>>
>> Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
>> this should go through mm.
> 
> Gentle ping on this series, it seems like it's better if it goes
> through your tree.
> 
> Series still applies cleanly on linux-next, but I'm happy to resend if
> that helps.

Ping, Andrew?

> Thanks!
> 
>> Regards,
>>
>>         Joerg
>
Nicolas Boichat Feb. 25, 2019, 12:23 a.m. UTC | #4
On Thu, Feb 14, 2019 at 1:12 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 1/22/19 11:51 PM, Nicolas Boichat wrote:
> > Hi Andrew,
> >
> > On Fri, Jan 11, 2019 at 6:21 PM Joerg Roedel <joro@8bytes.org> wrote:
> >>
> >> On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
> >> > Does anyone have any further comment on this series? If not, which
> >> > maintainer is going to pick this up? I assume Andrew Morton?
> >>
> >> Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
> >> this should go through mm.
> >
> > Gentle ping on this series, it seems like it's better if it goes
> > through your tree.
> >
> > Series still applies cleanly on linux-next, but I'm happy to resend if
> > that helps.
>
> Ping, Andrew?

Another gentle ping, I still don't see these patches in mmot[ms]. Thanks.

> > Thanks!
> >
> >> Regards,
> >>
> >>         Joerg
> >
>
Nicolas Boichat March 19, 2019, 7:41 a.m. UTC | #5
On Mon, Feb 25, 2019 at 8:23 AM Nicolas Boichat <drinkcat@chromium.org> wrote:
>
> On Thu, Feb 14, 2019 at 1:12 AM Vlastimil Babka <vbabka@suse.cz> wrote:
> >
> > On 1/22/19 11:51 PM, Nicolas Boichat wrote:
> > > Hi Andrew,
> > >
> > > On Fri, Jan 11, 2019 at 6:21 PM Joerg Roedel <joro@8bytes.org> wrote:
> > >>
> > >> On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
> > >> > Does anyone have any further comment on this series? If not, which
> > >> > maintainer is going to pick this up? I assume Andrew Morton?
> > >>
> > >> Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
> > >> this should go through mm.
> > >
> > > Gentle ping on this series, it seems like it's better if it goes
> > > through your tree.
> > >
> > > Series still applies cleanly on linux-next, but I'm happy to resend if
> > > that helps.
> >
> > Ping, Andrew?
>
> Another gentle ping, I still don't see these patches in mmot[ms]. Thanks.

Andrew: AFAICT this still applies cleanly on linux-next/master, so I
don't plan to resend... is there any other issues with this series?

This is a regression, so it'd be nice to have it fixed in mainline, eventually.

Thanks,

> > > Thanks!
> > >
> > >> Regards,
> > >>
> > >>         Joerg
> > >
> >
Andrew Morton March 19, 2019, 5:56 p.m. UTC | #6
On Tue, 19 Mar 2019 15:41:43 +0800 Nicolas Boichat <drinkcat@chromium.org> wrote:

> On Mon, Feb 25, 2019 at 8:23 AM Nicolas Boichat <drinkcat@chromium.org> wrote:
> >
> > On Thu, Feb 14, 2019 at 1:12 AM Vlastimil Babka <vbabka@suse.cz> wrote:
> > >
> > > On 1/22/19 11:51 PM, Nicolas Boichat wrote:
> > > > Hi Andrew,
> > > >
> > > > On Fri, Jan 11, 2019 at 6:21 PM Joerg Roedel <joro@8bytes.org> wrote:
> > > >>
> > > >> On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
> > > >> > Does anyone have any further comment on this series? If not, which
> > > >> > maintainer is going to pick this up? I assume Andrew Morton?
> > > >>
> > > >> Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
> > > >> this should go through mm.
> > > >
> > > > Gentle ping on this series, it seems like it's better if it goes
> > > > through your tree.
> > > >
> > > > Series still applies cleanly on linux-next, but I'm happy to resend if
> > > > that helps.
> > >
> > > Ping, Andrew?
> >
> > Another gentle ping, I still don't see these patches in mmot[ms]. Thanks.
> 
> Andrew: AFAICT this still applies cleanly on linux-next/master, so I
> don't plan to resend... is there any other issues with this series?
> 
> This is a regression, so it'd be nice to have it fixed in mainline, eventually.

Sorry, seeing "iommu" and "arm" made these escape my gimlet eye.

I'm only seeing acks on [1/3].  What's the review status of [2/3] and [3/3]?
Nicolas Boichat March 20, 2019, 12:20 a.m. UTC | #7
On Wed, Mar 20, 2019 at 1:56 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue, 19 Mar 2019 15:41:43 +0800 Nicolas Boichat <drinkcat@chromium.org> wrote:
>
> > On Mon, Feb 25, 2019 at 8:23 AM Nicolas Boichat <drinkcat@chromium.org> wrote:
> > >
> > > On Thu, Feb 14, 2019 at 1:12 AM Vlastimil Babka <vbabka@suse.cz> wrote:
> > > >
> > > > On 1/22/19 11:51 PM, Nicolas Boichat wrote:
> > > > > Hi Andrew,
> > > > >
> > > > > On Fri, Jan 11, 2019 at 6:21 PM Joerg Roedel <joro@8bytes.org> wrote:
> > > > >>
> > > > >> On Wed, Jan 02, 2019 at 01:51:45PM +0800, Nicolas Boichat wrote:
> > > > >> > Does anyone have any further comment on this series? If not, which
> > > > >> > maintainer is going to pick this up? I assume Andrew Morton?
> > > > >>
> > > > >> Probably, yes. I don't like to carry the mm-changes in iommu-tree, so
> > > > >> this should go through mm.
> > > > >
> > > > > Gentle ping on this series, it seems like it's better if it goes
> > > > > through your tree.
> > > > >
> > > > > Series still applies cleanly on linux-next, but I'm happy to resend if
> > > > > that helps.
> > > >
> > > > Ping, Andrew?
> > >
> > > Another gentle ping, I still don't see these patches in mmot[ms]. Thanks.
> >
> > Andrew: AFAICT this still applies cleanly on linux-next/master, so I
> > don't plan to resend... is there any other issues with this series?
> >
> > This is a regression, so it'd be nice to have it fixed in mainline, eventually.
>
> Sorry, seeing "iommu" and "arm" made these escape my gimlet eye.

Thanks for picking them up!

> I'm only seeing acks on [1/3].  What's the review status of [2/3] and [3/3]?

Replied on the notification, [2/3] had a Ack, [3/3] is somewhat controversial.