Similar to commit ac0e331a ("drm/i915: Tighten atomicity of
i915_active_acquire vs i915_active_release") we have the same race of
trying to pin the context underneath a mutex while allowing the
decrement to be atomic outside of that mutex. This leads to the problem
where two threads may simultaneously try to pin the context and the
second not notice that they needed to repin the context.

<2> [198.669621] kernel BUG at drivers/gpu/drm/i915/gt/intel_timeline.c:387!
<4> [198.669703] invalid opcode: 0000 [#1] PREEMPT SMP PTI
<4> [198.669712] CPU: 0 PID: 1246 Comm: gem_exec_create Tainted: G     U  W         5.5.0-rc6-CI-CI_DRM_7755+ #1
<4> [198.669723] Hardware name:  /NUC7i5BNB, BIOS BNKBL357.86A.0054.2017.1025.1822 10/25/2017
<4> [198.669776] RIP: 0010:timeline_advance+0x7b/0xe0 [i915]
<4> [198.669785] Code: 00 48 c7 c2 10 f1 46 a0 48 c7 c7 70 1b 32 a0 e8 bb dd e7 e0 bf 01 00 00 00 e8 d1 af e7 e0 31 f6 bf 09 00 00 00 e8 35 ef d8 e0 <0f> 0b 48 c7 c1 48 fa 49 a0 ba 84 01 00 00 48 c7 c6 10 f1 46 a0 48
<4> [198.669803] RSP: 0018:ffffc900004c3a38 EFLAGS: 00010296
<4> [198.669810] RAX: ffff888270b35140 RBX: ffff88826f32ee00 RCX: 0000000000000006
<4> [198.669818] RDX: 00000000000017c5 RSI: 0000000000000000 RDI: 0000000000000009
<4> [198.669826] RBP: ffffc900004c3a64 R08: 0000000000000000 R09: 0000000000000000
<4> [198.669834] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88826f9b5980
<4> [198.669841] R13: 0000000000000cc0 R14: ffffc900004c3dc0 R15: ffff888253610068
<4> [198.669849] FS:  00007f63e663fe40(0000) GS:ffff888276c00000(0000) knlGS:0000000000000000
<4> [198.669857] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4> [198.669864] CR2: 00007f171f8e39a8 CR3: 000000026b1f6005 CR4: 00000000003606f0
<4> [198.669872] Call Trace:
<4> [198.669924]  intel_timeline_get_seqno+0x12/0x40 [i915]
<4> [198.669977]  __i915_request_create+0x76/0x5a0 [i915]
<4> [198.670024]  i915_request_create+0x86/0x1c0 [i915]
<4> [198.670068]  i915_gem_do_execbuffer+0xbf2/0x2500 [i915]
<4> [198.670082]  ? __lock_acquire+0x460/0x15d0
<4> [198.670128]  i915_gem_execbuffer2_ioctl+0x11f/0x470 [i915]
<4> [198.670171]  ? i915_gem_execbuffer_ioctl+0x300/0x300 [i915]
<4> [198.670181]  drm_ioctl_kernel+0xa7/0xf0
<4> [198.670188]  drm_ioctl+0x2e1/0x390
<4> [198.670233]  ? i915_gem_execbuffer_ioctl+0x300/0x300 [i915]

Fixes: 84135022 ("drm/i915/gt: Drop mutex serialisation between context pin/unpin")
References: ac0e331a ("drm/i915: Tighten atomicity of i915_active_acquire vs i915_active_release")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200127152829.2842149-1-chris@chris-wilson.co.uk

As we use the active state to keep the vma alive while we are reading
its contents during GPU error capture, we need to mark the
ring->vma as active during execution if we want to include the rinbuffer
in the error state.
Reported-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: b1e3177b ("drm/i915: Coordinate i915_active with its own mutex")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200110110402.1231745-3-chris@chris-wilson.co.uk

As we use the active state to keep the vma alive while we are reading
its contents during GPU error capture, we need to mark the
context->state vma as active during execution if we want to include it
in the error state.
Reported-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: b1e3177b ("drm/i915: Coordinate i915_active with its own mutex")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200110110402.1231745-2-chris@chris-wilson.co.uk

Now that we have moved the runtime-pm management out of
intel_context_acctive_acquire, and that itself out of ce->ops->pin(), no
explicit runtime pm wakeref is required in intel_context_pin().
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200109085717.873326-3-chris@chris-wilson.co.uk

While this is encroaching on midlayer territory, having already made the
state allocation a previous step in pinning, we can now pull the common
intel_context_active_acquire() into intel_context_pin() itself. This is
a prelude to make the activation a separate step inside pinning, outside
of the ce->pin_mutex
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200109085717.873326-2-chris@chris-wilson.co.uk

Allow for knowledgeable users to preallocate the context state, and to
separate the allocation step from the pinning step during
intel_context_pin()
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200109085717.873326-1-chris@chris-wilson.co.uk

The last remaining reason for serialising the pin/unpin of the
intel_context is to ensure that our preallocated wakerefs are not
consumed too early (i.e. the unpin of the previous phase does not emit
the idle barriers for this phase before we even submit). All of the
other operations within the context pin/unpin are supposed to be
atomic...  Therefore, we can reduce the serialisation to being just on
the i915_active.preallocated_barriers itself and drop the nested
pin_mutex from intel_context_unpin().
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200106114234.2529613-5-chris@chris-wilson.co.uk

Convert the few remaining GEM_TRACE() used for debugging over to the
appropriate GT_TRACE or RQ_TRACE.

References: 639f2f24 ("drm/i915: Introduce new macros for tracing")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200106114234.2529613-4-chris@chris-wilson.co.uk

Allocate only an internal intel_context for the kernel_context, forgoing
a global GEM context for internal use as we only require a separate
address space (for our own protection).

Now having weaned GT from requiring ce->gem_context, we can stop
referencing it entirely. This also means we no longer have to create random
and unnecessary GEM contexts for internal use.

GEM contexts are now entirely for tracking GEM clients, and intel_context
the execution environment on the GPU.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Acked-by: NAndi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191221160324.1073045-1-chris@chris-wilson.co.uk

Instead of rummaging through the intel_context to peek at the GEM
context in the middle of request submission to decide whether to use
semaphores, store that information on the intel_context itself.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: NAndi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191220101230.256839-2-chris@chris-wilson.co.uk

Keep the intel_context as being the primary state for i915_request, with
the GEM context a backpointer from the low level state for the rarer
cases we need client information. Our goal is to remove such references
to clients from the backend, and leave the HW submission agnostic to
client interfaces and self-contained.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: NAndi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191220101230.256839-1-chris@chris-wilson.co.uk

New macros ENGINE_TRACE(), CE_TRACE(), RQ_TRACE() and
GT_TRACE() are introduce to tag device name and engine
name with contexts and requests tracing in i915.

Cc: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: NVenkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191213155152.69182-2-venkata.s.dhanalakota@intel.com

It is not acceptable for context pinning to fail with -ENOSPC as we
should always be able to make space in the GGTT. The only reason we may
fail is that other "temporary" context pins are reserving their space
and we need to wait for an available slot.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/676Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191205113726.413351-2-chris@chris-wilson.co.uk

Rather than assume if and only if the engine->default_state is not set
that the context is invalid, instead track when we know the context has
valid state -- either because we have copied the default_state or we
have completed a context switch to save the HW state.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191203124155.3019926-1-chris@chris-wilson.co.uk

The expected downside to commit 58b4c1a0 ("drm/i915: Reduce nested
prepare_remote_context() to a trylock") was that it would need to return
-EAGAIN to userspace in order to resolve potential mutex inversion. Such
an unsightly round trip is unnecessary if we could atomically insert a
barrier into the i915_active_fence, so make it happen.

Currently, we use the timeline->mutex (or some other named outer lock)
to order insertion into the i915_active_fence (and so individual nodes
of i915_active). Inside __i915_active_fence_set, we only need then
serialise with the interrupt handler in order to claim the timeline for
ourselves.

However, if we remove the outer lock, we need to ensure the order is
intact between not only multiple threads trying to insert themselves
into the timeline, but also with the interrupt handler completing the
previous occupant. We use xchg() on insert so that we have an ordered
sequence of insertions (and each caller knows the previous fence on
which to wait, preserving the chain of all fences in the timeline), but
we then have to cmpxchg() in the interrupt handler to avoid overwriting
the new occupant. The only nasty side-effect is having to temporarily
strip off the RCU-annotations to apply the atomic operations, otherwise
the rules are much more conventional!

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112402
Fixes: 58b4c1a0 ("drm/i915: Reduce nested prepare_remote_context() to a trylock")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191127134527.3438410-1-chris@chris-wilson.co.uk

On context retiring, we may invoke the kernel_context to unpin this
context. Elsewhere, we may use the kernel_context to modify this
context. This currently leads to an AB-BA lock inversion, so we need to
back-off from the contended lock, and repeat.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111732Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Fixes: a9877da2 ("drm/i915/oa: Reconfigure contexts on the fly")
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191126065521.2331017-1-chris@chris-wilson.co.uk
(cherry picked from commit 58b4c1a0)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

On context retiring, we may invoke the kernel_context to unpin this
context. Elsewhere, we may use the kernel_context to modify this
context. This currently leads to an AB-BA lock inversion, so we need to
back-off from the contended lock, and repeat.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111732Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Fixes: a9877da2 ("drm/i915/oa: Reconfigure contexts on the fly")
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191126065521.2331017-1-chris@chris-wilson.co.uk

Split the legacy submission backend from the common CS ring buffer
handling.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191024100344.5041-1-chris@chris-wilson.co.uk

Avoid going to the base i915 device when we already have a path from gt
to the runtime powermanagement interface. The benefit is that it looks a
bit more self-consistent to always be acquiring the gt->uncore->rpm for
use with the gt->uncore.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191007154531.1750-1-chris@chris-wilson.co.uk

Keep track of the GEM contexts underneath i915->gem.contexts and assign
them their own lock for the purposes of list management.

v2: Focus on lock tracking; ctx->vm is protected by ctx->mutex
v3: Correct split with removal of logical HW ID
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-15-chris@chris-wilson.co.uk

Forgo the struct_mutex serialisation for i915_active, and interpose its
own mutex handling for active/retire.

This is a multi-layered sleight-of-hand. First, we had to ensure that no
active/retire callbacks accidentally inverted the mutex ordering rules,
nor assumed that they were themselves serialised by struct_mutex. More
challenging though, is the rule over updating elements of the active
rbtree. Instead of the whole i915_active now being serialised by
struct_mutex, allocations/rotations of the tree are serialised by the
i915_active.mutex and individual nodes are serialised by the caller
using the i915_timeline.mutex (we need to use nested spinlocks to
interact with the dma_fence callback lists).

The pain point here is that instead of a single mutex around execbuf, we
now have to take a mutex for active tracker (one for each vma, context,
etc) and a couple of spinlocks for each fence update. The improvement in
fine grained locking allowing for multiple concurrent clients
(eventually!) should be worth it in typical loads.

v2: Add some comments that barely elucidate anything :(
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-6-chris@chris-wilson.co.uk

As we need to use a mutex to serialise i915_active activation
(because we want to allow the callback to sleep), we need to push the
i915_active.retire into a worker callback in case we get need to retire
from an atomic context.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-5-chris@chris-wilson.co.uk

The request->timeline is only valid until the request is retired (i.e.
before it is completed). Upon retiring the request, the context may be
unpinned and freed, and along with it the timeline may be freed. We
therefore need to be very careful when chasing rq->timeline that the
pointer does not disappear beneath us. The vast majority of users are in
a protected context, either during request construction or retirement,
where the timeline->mutex is held and the timeline cannot disappear. It
is those few off the beaten path (where we access a second timeline) that
need extra scrutiny -- to be added in the next patch after first adding
the warnings about dangerous access.

One complication, where we cannot use the timeline->mutex itself, is
during request submission onto hardware (under spinlocks). Here, we want
to check on the timeline to finalize the breadcrumb, and so we need to
impose a second rule to ensure that the request->timeline is indeed
valid. As we are submitting the request, it's context and timeline must
be pinned, as it will be used by the hardware. Since it is pinned, we
know the request->timeline must still be valid, and we cannot submit the
idle barrier until after we release the engine->active.lock, ergo while
submitting and holding that spinlock, a second thread cannot release the
timeline.

v2: Don't be lazy inside selftests; hold the timeline->mutex for as long
as we need it, and tidy up acquiring the timeline with a bit of
refactoring (i915_active_add_request)
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190919111912.21631-1-chris@chris-wilson.co.uk

Add an atomic counter and always take the spinlock around the pin/unpin
events, so that we can perform the list manipulation concurrently.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190910212204.17190-1-chris@chris-wilson.co.uk

As every i915_active_request should be serialised by a dedicated lock,
i915_active consists of a tree of locks; one for each node. Markup up
the i915_active_request with what lock is supposed to be guarding it so
that we can verify that the serialised updated are indeed serialised.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190816121000.8507-2-chris@chris-wilson.co.uk

Lift moving the timeline to/from the active_list on enter/exit in order
to shorten the active tracking span in comparison to the existing
pin/unpin.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190815205709.24285-1-chris@chris-wilson.co.uk

Move the timeline from being inside the intel_ring to intel_context
itself. This saves much pointer dancing and makes the relations of the
context to its timeline much clearer.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190809182518.20486-4-chris@chris-wilson.co.uk

Push the ring creation flags from the outer GEM context to the inner
intel_context to avoid an unsightly back-reference from inside the
backend.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NAndi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190809182518.20486-3-chris@chris-wilson.co.uk

Refactor the backends to handle the deferred context allocation in a
consistent manner, and allow calling it as an explicit first step in
pinning a context for the first time. This should make it easier for
backends to keep track of partially constructed contexts from
initialisation.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190809182518.20486-2-chris@chris-wilson.co.uk

The shrinker cannot touch objects used by the contexts (logical state
and ring). Currently we mark those as "pin_global" to let the shrinker
skip over them, however, if we remove them from the shrinker lists
entirely, we don't event have to include them in our shrink accounting.

By keeping the unshrinkable objects in our shrinker tracking, we report
a large number of objects available to be shrunk, and leave the shrinker
deeply unsatisfied when we fail to reclaim those. The shrinker will
persist in trying to reclaim the unavailable objects, forcing the system
into a livelock (not even hitting the dread oomkiller).

v2: Extend unshrinkable protection for perma-pinned scratch and guc
allocations (Tvrtko)
v3: Notice that we should be pinned when marking unshrinkable and so the
link cannot be empty; merge duplicate paths.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190802212137.22207-1-chris@chris-wilson.co.uk

By placing our idle-barriers in the i915_active fence tree, we expose
those for reuse by other components that are issuing requests along the
kernel_context. Reusing the proto-barrier active_node is perfectly fine
as the new request implies a context-switch, and so an opportune point
to run the idle-barrier. However, the proto-barrier is not equivalent
to a normal active_node and care must be taken to avoid dereferencing the
ERR_PTR used as its request marker.

v2: Comment the more egregious cheek
v3: A glossary!
Reported-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: ce476c80 ("drm/i915: Keep contexts pinned until after the next kernel context switch")
Fixes: a9877da2 ("drm/i915/oa: Reconfigure contexts on the fly")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190802100015.1281-1-chris@chris-wilson.co.uk

Track the currently bound address space used by the HW context. Minor
conversions to use the local intel_context.vm are made, leaving behind
some more surgery required to make intel_context the primary through the
selftests.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190730143209.4549-2-chris@chris-wilson.co.uk

Remember to keep the rings pinned as well as the context image until the
GPU is no longer active.

v2: Introduce a ring->pin_count primarily to hide the
mock_ring that doesn't fit into the normal GGTT vma picture.

v3: Order is important in teardown, ringbuffer submission needs to drop
the pin count on the engine->kernel_context before it can gleefully free
its ring.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110946
Fixes: ce476c80 ("drm/i915: Keep contexts pinned until after the next kernel context switch")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190619170135.15281-1-chris@chris-wilson.co.uk
(cherry picked from commit 09c5ab38)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Modifying a remote context requires careful serialisation with requests
on that context, and that serialisation requires us to take their
timeline->mutex. Make it so.

Note that while struct_mutex rules, we can't create more than one
request in parallel, but that age is soon coming to an end.

v2: Though it doesn't affect the current users, contexts may share
timelines so check if we already hold the right mutex.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190725131447.27515-1-chris@chris-wilson.co.uk

Prior to freeing the struct, call the fini function to cleanup the
common members. Currently this only calls the debug functions to mark
the structs as destroyed, but may be extended to real work in future.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190718070024.21781-2-chris@chris-wilson.co.uk

Avoid a global idle barrier by reconfiguring each context by rewriting
them with MI_STORE_DWORD from the kernel context.

v2: We only need to determine the desired register values once, they are
the same for all contexts.
v3: Don't remove the kernel context from the list of known GEM contexts;
the world is not ready for that yet.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190716213443.9874-1-chris@chris-wilson.co.uk

Add the context pin/unpin events to the trace for post-mortem debugging.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190625194859.28005-1-chris@chris-wilson.co.uk

If we introduce a callback for i915_active that is only called the first
time we use the i915_active and is symmetrically paired with the
i915_active.retire callback, we can replace the open-coded and
non-atomic implementations -- which will be very fragile (i.e. broken)
upon removing the struct_mutex serialisation.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190621183801.23252-4-chris@chris-wilson.co.uk

Remember to keep the rings pinned as well as the context image until the
GPU is no longer active.

v2: Introduce a ring->pin_count primarily to hide the
mock_ring that doesn't fit into the normal GGTT vma picture.

v3: Order is important in teardown, ringbuffer submission needs to drop
the pin count on the engine->kernel_context before it can gleefully free
its ring.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110946
Fixes: ce476c80 ("drm/i915: Keep contexts pinned until after the next kernel context switch")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190619170135.15281-1-chris@chris-wilson.co.uk

The idea behind keeping the saturation mask local to a context backfired
spectacularly. The premise with the local mask was that we would be more
proactive in attempting to use semaphores after each time the context
idled, and that all new contexts would attempt to use semaphores
ignoring the current state of the system. This turns out to be horribly
optimistic. If the system state is still oversaturated and the existing
workloads have all stopped using semaphores, the new workloads would
attempt to use semaphores and be deprioritised behind real work. The
new contexts would not switch off using semaphores until their initial
batch of low priority work had completed. Given sufficient backload load
of equal user priority, this would completely starve the new work of any
GPU time.

To compensate, remove the local tracking in favour of keeping it as
global state on the engine -- once the system is saturated and
semaphores are disabled, everyone stops attempting to use semaphores
until the system is idle again. One of the reason for preferring local
context tracking was that it worked with virtual engines, so for
switching to global state we could either do a complete check of all the
virtual siblings or simply disable semaphores for those requests. This
takes the simpler approach of disabling semaphores on virtual engines.

The downside is that the decision that the engine is saturated is a
local measure -- we are only checking whether or not this context was
scheduled in a timely fashion, it may be legitimately delayed due to user
priorities. We still have the same dilemma though, that we do not want
to employ the semaphore poll unless it will be used.

v2: Explain why we need to assume the worst wrt virtual engines.

Fixes: ca6e56f6 ("drm/i915: Disable semaphore busywaits on saturated systems")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
Cc: Dmitry Ermilov <dmitry.ermilov@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190618074153.16055-8-chris@chris-wilson.co.uk