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  1. 13 Sep, 2021 8 commits
  3. 10 Sep, 2021 2 commits
    • Vinay Belgaumkar's avatar
      drm/i915: Get PM ref before accessing HW register · f25e3908
      Vinay Belgaumkar authored 
      Seeing these errors when GT is likely in suspend state-
"RPM wakelock ref not held during HW access"

Ensure GT is awake before trying to access HW registers. Avoid
reading the register if that is not the case.
Signed-off-by: default avatarVinay Belgaumkar <vinay.belgaumkar@intel.com>
Fixes: 41e5c17e ("drm/i915/guc/slpc: Sysfs hooks for SLPC")
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210907232704.12982-1-vinay.belgaumkar@intel.com
      f25e3908
    • Tvrtko Ursulin's avatar
      drm/i915: Use Transparent Hugepages when IOMMU is enabled · 74388ca4
      Tvrtko Ursulin authored 
      Usage of Transparent Hugepages was disabled in 9987da4b
("drm/i915: Disable THP until we have a GPU read BW W/A"), but since it
appears majority of performance regressions reported with an enabled IOMMU
can be almost eliminated by turning them on, lets just do that.

To err on the side of safety we keep the current default in cases where
IOMMU is not active, and only when it is default to the "huge=within_size"
mode. Although there probably would be wins to enable them throughout,
more extensive testing across benchmarks and platforms would need to be
done.

With the patch and IOMMU enabled my local testing on a small Skylake part
shows OglVSTangent regression being reduced from ~14% (IOMMU on versus
IOMMU off) to ~2% (same comparison but with THP on).

More detailed testing done in the below referenced Gitlab issue by Eero:

Skylake GT4e:

Performance drops from enabling IOMMU:

    30-35% SynMark CSDof
    20-25% Unigine Heaven, MemBW GPU write, SynMark VSTangent
    ~20% GLB Egypt  (1/2 screen window)
    10-15% GLB T-Rex (1/2 screen window)
    8-10% GfxBench T-Rex, MemBW GPU blit
    7-8% SynMark DeferredAA + TerrainFly* + ZBuffer
    6-7% GfxBench Manhattan 3.0 + 3.1, SynMark TexMem128 & CSCloth
    5-6% GfxBench CarChase, Unigine Valley
    3-5% GfxBench Vulkan & GL AztecRuins + ALU2, MemBW GPU texture,
         SynMark Fill*, Deferred, TerrainPan*
    1-2% Most of the other tests

With the patch drops become:

    20-25% SynMark TexMem*
    15-20% GLB Egypt (1/2 screen window)
    10-15% GLB T-Rex (1/2 screen window)
    4-7% GfxBench T-Rex, GpuTest Triangle
    1-8% GfxBench ALU2 (offscreen 1%, onscreen 8%)
    3% GfxBench Manhattan 3.0, SynMark CSDof
    2-3% Unigine Heaven + Valley, MemBW GPU texture
    1-3 GfxBench Manhattan 3.1 + CarChase + Vulkan & GL AztecRuins

Broxton:

Performance drops from IOMMU, without patch:

    30% MemBW GPU write
    25% SynMark ZBuffer + Fill*
    20% MemBW GPU blit
    15% MemBW GPU blend, GpuTest Triangle
    10-15% MemBW GPU texture
    10% GLB Egypt, Unigine Heaven (had hangs), SynMark TerrainFly*
    7-9% GLB T-Rex, GfxBench Manhattan 3.0 + T-Rex,
         SynMark Deferred* + TexMem*
    6-8% GfxBench CarChase, Unigine Valley,
         SynMark CSCloth + ShMapVsm + TerrainPan*
    5-6% GfxBench Manhattan 3.1 + GL AztecRuins,
         SynMark CSDof + TexFilterTri
    2-4% GfxBench ALU2, SynMark DrvRes + GSCloth + ShMapPcf + Batch[0-5] +
         TexFilterAniso, GpuTest GiMark + 32-bit Julia

And with patch:

    15-20% MemBW GPU texture
    10% SynMark TexMem*
    8-9% GLB Egypt (1/2 screen window)
    4-5% GLB T-Rex (1/2 screen window)
    3-6% GfxBench Manhattan 3.0, GpuTest FurMark,
         SynMark Deferred + TexFilterTri
    3-4% GfxBench Manhattan 3.1 + T-Rex, SynMark VSInstancing
    2-4% GpuTest Triangle, SynMark DeferredAA
    2-3% Unigine Heaven + Valley
    1-3% SynMark Terrain*
    1-2% GfxBench CarChase, SynMark TexFilterAniso + ZBuffer

Tigerlake-H:

    20-25% MemBW GPU texture
    15-20% GpuTest Triangle
    13-15% SynMark TerrainFly* + DeferredAA + HdrBloom
    8-10% GfxBench Manhattan 3.1, SynMark TerrainPan* + DrvRes
    6-7% GfxBench Manhattan 3.0, SynMark TexMem*
    4-8% GLB onscreen Fill + T-Rex + Egypt (more in onscreen than
         offscreen versions of T-Rex/Egypt)
    4-6% GfxBench CarChase + GLES AztecRuins + ALU2, GpuTest 32-bit Julia,
         SynMark CSDof + DrvState
    3-5% GfxBench T-Rex + Egypt, Unigine Heaven + Valley, GpuTest Plot3D
    1-7% Media tests
    2-3% MemBW GPU blit
    1-3% Most of the rest of 3D tests

With the patch:

    6-8% MemBW GPU blend => the only regression in these tests (compared
         to IOMMU without THP)
    4-6% SynMark DrvState (not impacted) + HdrBloom (improved)
    3-4% GLB T-Rex
    ~3% GLB Egypt, SynMark DrvRes
    1-3% GfxBench T-Rex + Egypt, SynMark TexFilterTri
    1-2% GfxBench CarChase + GLES AztecRuins, Unigine Valley,
        GpuTest Triangle
    ~1% GfxBench Manhattan 3.0/3.1, Unigine Heaven

Perf of several tests actually improved with IOMMU + THP, compared to no
IOMMU / no THP:

    10-15% SynMark Batch[0-3]
    5-10% MemBW GPU texture, SynMark ShMapVsm
    3-4% SynMark Fill* + Geom*
    2-3% SynMark TexMem512 + CSCloth
    1-2% SynMark TexMem128 + DeferredAA

As a summary across all platforms, these are the benchmarks where enabling
THP on top of IOMMU enabled brings regressions:

 * Skylake GT4e:
   20-25% SynMark TexMem*
   (whereas all MemBW GPU tests either improve or are not affected)

 * Broxton J4205:
   7% MemBW GPU texture
   2-3% SynMark TexMem*

 * Tigerlake-H:
   7% MemBW GPU blend

Other benchmarks show either lowering of regressions or improvements.

v2:
 * Add Kconfig dependency to transparent hugepages and some help text.
 * Move to helper for easier handling of kernel build options.

v3:
 * Drop Kconfig. (Daniel)

v4:
 * Add some benchmark results to commit message.

v5:
 * Add explicit regression summary to commit message. (Eero)

References: b901bb89 ("drm/i915/gemfs: enable THP")
References: 9987da4b ("drm/i915: Disable THP until we have a GPU read BW W/A")
References: https://gitlab.freedesktop.org/drm/intel/-/issues/430Co-developed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Eero Tamminen <eero.t.tamminen@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210909114448.508493-1-tvrtko.ursulin@linux.intel.com
      74388ca4
  5. 08 Sep, 2021 4 commits
  7. 07 Sep, 2021 1 commit
  9. 06 Sep, 2021 11 commits
    • Daniel Vetter's avatar
      drm/i915: Stop rcu support for i915_address_space · dcc5d820
      Daniel Vetter authored 
      The full audit is quite a bit of work:

- i915_dpt has very simple lifetime (somehow we create a display pagetable vm
  per object, so its _very_ simple, there's only ever a single vma in there),
  and uses i915_vm_close(), which internally does a i915_vm_put(). No rcu.

  Aside: wtf is i915_dpt doing in the intel_display.c garbage collector as a new
  feature, instead of added as a separate file with some clean-ish interface.

  Also, i915_dpt unfortunately re-introduces some coding patterns from
  pre-dma_resv_lock conversion times.

- i915_gem_proto_ctx is fully refcounted and no rcu, all protected by
  fpriv->proto_context_lock.

- i915_gem_context is itself rcu protected, and that might leak to anything it
  points at. Before

	commit cf977e18
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Wed Dec 2 11:21:40 2020 +0000

	    drm/i915/gem: Spring clean debugfs

  and

	commit db80a129
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Mon Jan 18 11:08:54 2021 +0000

	    drm/i915/gem: Remove per-client stats from debugfs/i915_gem_objects

  we had a bunch of debugfs files that relied on rcu protecting everything, but
  those are gone now. The main one was removed even earlier with

  There doesn't seem to be anything left that's actually protecting
  stuff now that the ctx->vm itself is invariant. See

	commit ccbc1b97
	Author: Jason Ekstrand <jason@jlekstrand.net>
	Date:   Thu Jul 8 10:48:30 2021 -0500

	    drm/i915/gem: Don't allow changing the VM on running contexts (v4)

  Note that we drop the vm refcount before the final release of the gem context
  refcount, so this is all very dangerous even without rcu. Note that aside from
  later on creating new engines (a defunct feature) and debug output we're never
  looked at gem_ctx->vm for anything functional, hence why this is ok.
  Fingers crossed.

  Preceeding patches removed all vestiges of rcu use from gem_ctx->vm
  derferencing to make it clear it's really not used.

  The gem_ctx->rcu protection was introduced in

	commit a4e7ccda
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Fri Oct 4 14:40:09 2019 +0100

	    drm/i915: Move context management under GEM

  The commit message is somewhat entertaining because it fails to
  mention this fact completely, and compensates that by an in-commit
  changelog entry that claims that ctx->vm is protected by ctx->mutex.
  Which was the case _before_ this commit, but no longer after it.

- intel_context holds a full reference. Unfortunately intel_context is also rcu
  protected and the reference to the ->vm is dropped before the
  rcu barrier - only the kfree is delayed. So again we need to check
  whether that leaks anywhere on the intel_context->vm. RCU is only
  used to protect intel_context sitting on the breadcrumb lists, which
  don't look at the vm anywhere, so we are fine.

  Nothing else relies on rcu protection of intel_context and hence is
  fully protected by the kref refcount alone, which protects
  intel_context->vm in turn.

  The breadcrumbs rcu usage was added in

	commit c744d503
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Thu Nov 26 14:04:06 2020 +0000

	    drm/i915/gt: Split the breadcrumb spinlock between global and contexts

  its parent commit added the intel_context rcu protection:

	commit 14d1eaf0
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Thu Nov 26 14:04:05 2020 +0000

	    drm/i915/gt: Protect context lifetime with RCU

  given some credence to my claim that I've actually caught them all.

- drm_i915_gem_object's shares_resv_from pointer has a full refcount to the
  dma_resv, which is a sub-refcount that's released after the final
  i915_vm_put() has been called. Safe.

  Aside: Maybe we should have a struct dma_resv_shared which is just dma_resv +
  kref as a stand-alone thing. It's a pretty useful pattern which other drivers
  might want to copy.

  For a bit more context see

	commit 4d8151ae
	Author: Thomas Hellström <thomas.hellstrom@linux.intel.com>
	Date:   Tue Jun 1 09:46:41 2021 +0200

	    drm/i915: Don't free shared locks while shared

- the fpriv->vm_xa was relying on rcu_read_lock for lookup, but that
  was updated in a prep patch too to just be a spinlock-protected
  lookup.

- intel_gt->vm is set at driver load in intel_gt_init() and released
  in intel_gt_driver_release(). There seems to be some issue that
  in some error paths this is called twice, but otherwise no rcu to be
  found anywhere. This was added in the below commit, which
  unfortunately doesn't explain why this complication exists.

	commit e6ba7648
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Sat Dec 21 16:03:24 2019 +0000

	    drm/i915: Remove i915->kernel_context

  The proper fix most likely for this is to start using drmm_ at large
  scale, but that's also huge amounts of work.

- i915_vma->vm is some real pain, because rcu is rcu protected, at
  least in the vma lookup in the context lookup cache in
  eb_lookup_vma(). This was added in

	commit 4ff4b44c
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Fri Jun 16 15:05:16 2017 +0100

	    drm/i915: Store a direct lookup from object handle to vma

  This was changed to a radix tree from the hashtable in, but with the
  locking unchanged, in

	commit d1b48c1e
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Wed Aug 16 09:52:08 2017 +0100

	    drm/i915: Replace execbuf vma ht with an idr

  In

	commit 93159e12
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Mon Mar 23 09:28:41 2020 +0000

	    drm/i915/gem: Avoid gem_context->mutex for simple vma lookup

  the locking was changed from dev->struct_mutex to rcu, which added
  the requirement to rcu protect i915_vma. Somehow this was missed in
  review (or I'm completely blind).

  Irrespective of all that the vma lookup cache rcu_read_lock grabs a
  full reference of the vma and the rcu doesn't leak further. So no
  impact on i915_address_space from that.

  I have not found any other rcu use for i915_vma, but given that it
  seems broken I also didn't bother to do a careful in-depth audit.

Alltogether there's nothing left in-tree anymore which requires that a
pointer deref to an i915_address_space is safe undre rcu_read_lock
only.

rcu protection of i915_address_space was introduced in

commit b32fa811
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Jun 20 19:37:05 2019 +0100

    drm/i915/gtt: Defer address space cleanup to an RCU worker

by mixing up a bugfixing (i915_address_space needs to be released from
a worker) with enabling rcu support. The commit message also seems
somewhat confused, because it talks about cleanup of WC pages
requiring sleep, while the code and linked bugzilla are about a
requirement to take dev->struct_mutex (which yes sleeps but it's a
much more specific problem). Since final kref_put can be called from
pretty much anywhere (including hardirq context through the
scheduler's i915_active cleanup) we need a worker here. Hence that
part must be kept.

Ideally all these reclaim workers should have some kind of integration
with our shrinkers, but for some of these it's rather tricky. Anyway,
that's a preexisting condition in the codeebase that we wont fix in
this patch here.

We also remove the rcu_barrier in ggtt_cleanup_hw added in

commit 60a4233a
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Jul 29 14:24:12 2019 +0100

    drm/i915: Flush the i915_vm_release before ggtt shutdown
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-11-daniel.vetter@ffwll.ch
      dcc5d820
    • Daniel Vetter's avatar
      drm/i915: use xa_lock/unlock for fpriv->vm_xa lookups · 84315152
      Daniel Vetter authored 
      We don't need the absolute speed of rcu for this. And
i915_address_space in general dont need rcu protection anywhere else,
after we've made gem contexts and engines a lot more immutable.

Note that this semantically reverts

commit aabbe344
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Aug 30 19:03:25 2019 +0100

    drm/i915: Use RCU for unlocked vm_idr lookup

except we have the conversion from idr to xarray in between.

v2: kref_get_unless_zero is no longer required (Maarten)
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-10-daniel.vetter@ffwll.ch
      84315152
    • Daniel Vetter's avatar
      drm/i915: Drop __rcu from gem_context->vm · 9ec8795e
      Daniel Vetter authored 
      It's been invariant since

    commit ccbc1b97
    Author: Jason Ekstrand <jason@jlekstrand.net>
    Date:   Thu Jul 8 10:48:30 2021 -0500

        drm/i915/gem: Don't allow changing the VM on running contexts (v4)

this just completes the deed. I've tried to split out prep work for
more careful review as much as possible, this is what's left:

- get_ppgtt gets simplified since we don't need to grab a temporary
  reference - we can rely on the temporary reference for the gem_ctx
  while we inspect the vm. The new vm_id still needs a full
  i915_vm_open ofc. This also removes the final caller of context_get_vm_rcu

- A pile of selftests can now just look at ctx->vm instead of
  rcu_dereference_protected( , true) or similar things.

- All callers of i915_gem_context_vm also disappear.

- I've changed the hugepage selftest to set scrub_64K without any
  locking, because when we inspect that setting we're also not taking
  any locks either. It works because it's a selftests that's careful
  (single threaded gives you nice ordering) and not a live driver
  where races can happen from anywhere.

These can only be split up further if we have some intermediate state
with a bunch more rcu_dereference_protected(ctx->vm, true), just to
shut up lockdep and sparse.

The conversion to __rcu happened in

commit a4e7ccda
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Oct 4 14:40:09 2019 +0100

    drm/i915: Move context management under GEM

Note that we're not breaking the actual bugfix in there: The real
bugfix is pushing the i915_vm_relase onto a separate worker, to avoid
locking inversion issues. The rcu conversion was just thrown in for
entertainment value on top (no vm lookup isn't even close to anything
that's a hotpath where removing the single spinlock can be measured).

v2: Rebase over the change to move the i915_vm_put() into
i915_gem_context_release().

v3: Trivial conflict against repainted shed.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-9-daniel.vetter@ffwll.ch
      9ec8795e
    • Daniel Vetter's avatar
      drm/i915: Use i915_gem_context_get_eb_vm in intel_context_set_gem · 0483a301
      Daniel Vetter authored 
      Since

commit ccbc1b97
Author: Jason Ekstrand <jason@jlekstrand.net>
Date:   Thu Jul 8 10:48:30 2021 -0500

    drm/i915/gem: Don't allow changing the VM on running contexts (v4)

the gem_ctx->vm can't change anymore. Plus we always set the
intel_context->vm, so might as well use the helper we have for that.

This makes it very clear that we always overwrite intel_context->vm
for userspace contexts, since the default is gt->vm, which is
explicitly reserved for kernel context use. It would be good to split
things up a bit further and avoid any possibility for an accident
where we run kernel stuff in userspace vm or the other way round.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-8-daniel.vetter@ffwll.ch
      0483a301
    • Daniel Vetter's avatar
      drm/i915: Add i915_gem_context_is_full_ppgtt · a82a9979
      Daniel Vetter authored 
      And use it anywhere we have open-coded checks for ctx->vm that really
only check for full ppgtt.

Plus for paranoia add a GEM_BUG_ON that checks it's really only set
when we have full ppgtt, just in case. gem_context->vm is different
since it's NULL in ggtt mode, unlike intel_context->vm or gt->vm,
which is always set.

v2: 0day found a testcase that I missed.

v3: Repaint shed (Jon, Tvrtko)
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-7-daniel.vetter@ffwll.ch
      a82a9979
    • Daniel Vetter's avatar
      drm/i915: Use i915_gem_context_get_eb_vm in ctx_getparam · 24fad29e
      Daniel Vetter authored 
      Consolidates the "which is the vm my execbuf runs in" code a bit. We
do some get/put which isn't really required, but all the other users
want the refcounting, and I figured doing a function just for this
getparam to avoid 2 atomis is a bit much.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-6-daniel.vetter@ffwll.ch
      24fad29e
    • Daniel Vetter's avatar
      drm/i915: Rename i915_gem_context_get_vm_rcu to i915_gem_context_get_eb_vm · c6d04e48
      Daniel Vetter authored 
      The important part isn't so much that this does an rcu lookup - that's
more an implementation detail, which will also be removed.

The thing that makes this different from other functions is that it's
gettting you the vm that batchbuffers will run in for that gem
context, which is either a full ppgtt stored in gem->ctx, or the ggtt.

We'll make more use of this function later on.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-5-daniel.vetter@ffwll.ch
      c6d04e48
    • Daniel Vetter's avatar
      drm/i915: Drop code to handle set-vm races from execbuf · e1068a9e
      Daniel Vetter authored 
      Changing the vm from a finalized gem ctx is no longer possible, which
means we don't have to check for that anymore.

I was pondering whether to keep the check as a WARN_ON, but things go
boom real bad real fast if the vm of a vma is wrong. Plus we'd need to
also get the ggtt vm for !full-ppgtt platforms. Ditching it all seemed
like a better idea.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
References: ccbc1b97 ("drm/i915/gem: Don't allow changing the VM on running contexts (v4)")
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-4-daniel.vetter@ffwll.ch
      e1068a9e
    • Daniel Vetter's avatar
      drm/i915: Keep gem ctx->vm alive until the final put · 8cf97637
      Daniel Vetter authored 
      The comment added in

    commit b81dde71
    Author: Chris Wilson <chris@chris-wilson.co.uk>
    Date:   Tue May 21 22:11:29 2019 +0100

        drm/i915: Allow userspace to clone contexts on creation

and moved in

    commit 27dbae8f
    Author: Chris Wilson <chris@chris-wilson.co.uk>
    Date:   Wed Nov 6 09:13:12 2019 +0000

        drm/i915/gem: Safely acquire the ctx->vm when copying

suggested that i915_address_space were at least intended to be managed
through SLAB_TYPESAFE_BY_RCU:

                * This ppgtt may have be reallocated between
                * the read and the kref, and reassigned to a third
                * context. In order to avoid inadvertent sharing
                * of this ppgtt with that third context (and not
                * src), we have to confirm that we have the same
                * ppgtt after passing through the strong memory
                * barrier implied by a successful
                * kref_get_unless_zero().

But extensive git history search has not brough any such reuse to
light.

What has come to light though is that ever since

commit 2850748e
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Oct 4 14:39:58 2019 +0100

    drm/i915: Pull i915_vma_pin under the vm->mutex

(yes this commit is earlier) the final i915_vma_put call has been
moved from i915_gem_context_free (now called _release) to
context_close, which means it's not actually safe anymore to access
the ctx->vm pointer without lock helds, because it might disappear at
any moment. Note that superficially things all still work, because the
i915_address_space is RCU protected since

    commit b32fa811
    Author: Chris Wilson <chris@chris-wilson.co.uk>
    Date:   Thu Jun 20 19:37:05 2019 +0100

        drm/i915/gtt: Defer address space cleanup to an RCU worker

except the very clever macro above (which is designed to protected
against object reuse due to SLAB_TYPESAFE_BY_RCU or similar tricks)
results in an endless loop if the refcount of the ctx->vm ever
permanently drops to 0. Which it totally now can.

Fix that by moving the final i915_vm_put to where it should be.

Note that i915_gem_context is rcu protected, but _only_ the final
kfree. This means anyone who chases a pointer to a gem ctx solely
under the protection can pretty only call kref_get_unless_zero(). This
seems to be pretty much the case, aside from a bunch of cases that
consult the scheduling information without any further protection.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: "Thomas Hellström" <thomas.hellstrom@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Fixes: 2850748e ("drm/i915: Pull i915_vma_pin under the vm->mutex")
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-3-daniel.vetter@ffwll.ch
      8cf97637
    • Daniel Vetter's avatar
      drm/i915: Release ctx->syncobj on final put, not on ctx close · c238980e
      Daniel Vetter authored 
      gem context refcounting is another exercise in least locking design it
seems, where most things get destroyed upon context closure (which can
race with anything really). Only the actual memory allocation and the
locks survive while holding a reference.

This tripped up Jason when reimplementing the single timeline feature
in

commit 00dae4d3
Author: Jason Ekstrand <jason@jlekstrand.net>
Date:   Thu Jul 8 10:48:12 2021 -0500

    drm/i915: Implement SINGLE_TIMELINE with a syncobj (v4)

We could fix the bug by holding ctx->mutex in execbuf and clear the
pointer (again while holding the mutex) context_close, but it's
cleaner to just make the context object actually invariant over its
_entire_ lifetime. This way any other ioctl that's potentially racing,
but holding a full reference, can still rely on ctx->syncobj being
an immutable pointer. Which without this change, is not the case.
Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Fixes: 00dae4d3 ("drm/i915: Implement SINGLE_TIMELINE with a syncobj (v4)")
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: "Thomas Hellström" <thomas.hellstrom@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-2-daniel.vetter@ffwll.ch
      c238980e
    • Daniel Vetter's avatar
      drm/i915: Release i915_gem_context from a worker · 75eefd82
      Daniel Vetter authored 
      The only reason for this really is the i915_gem_engines->fence
callback engines_notify(), which exists purely as a fairly funky
reference counting scheme for that. Otherwise all other callers are
from process context, and generally fairly benign locking context.

Unfortunately untangling that requires some major surgery, and we have
a few i915_gem_context reference counting bugs that need fixing, and
they blow in the current hardirq calling context, so we need a
stop-gap measure.

Put a FIXME comment in when this should be removable again.

v2: Fix mock_context(), noticed by intel-gfx-ci.
Acked-by: default avatarAcked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902142057.929669-1-daniel.vetter@ffwll.ch
      75eefd82
  11. 03 Sep, 2021 5 commits
  13. 02 Sep, 2021 1 commit
  15. 31 Aug, 2021 1 commit
  17. 27 Aug, 2021 2 commits
  19. 26 Aug, 2021 1 commit
  21. 25 Aug, 2021 4 commits
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