[Intel-gfx] [PATCH 2/2] drm/i915: Reorganise legacy context switch to cope with late failure
Chris Wilson
chris at chris-wilson.co.uk
Wed Apr 13 14:16:31 UTC 2016
After mi_set_context() succeeds, we need to update the state of the
engine's last_context. This ensures that we hold a pin on the context
whilst the hardware may write to it. However, since we didn't complete
the post-switch setup of the context, we need to force the subsequent
use of the same context to complete the setup (which means updating
should_skip_switch()).
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
---
drivers/gpu/drm/i915/i915_gem_context.c | 147 ++++++++++++++++----------------
1 file changed, 74 insertions(+), 73 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index c027240aacf3..702780d9af57 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -609,18 +609,19 @@ mi_set_context(struct drm_i915_gem_request *req, u32 hw_flags)
return ret;
}
-static inline bool skip_rcs_switch(struct intel_engine_cs *engine,
- struct intel_context *from,
+static inline bool skip_rcs_switch(struct intel_context *from,
struct intel_context *to)
{
if (to->remap_slice)
return false;
- if (to->ppgtt && from == to &&
- !(intel_engine_flag(engine) & to->ppgtt->pd_dirty_rings))
- return true;
+ if (!to->legacy_hw_ctx.initialized)
+ return false;
- return false;
+ if (to->ppgtt && to->ppgtt->pd_dirty_rings & (1 << RCS))
+ return false;
+
+ return to == from;
}
static bool
@@ -643,18 +644,12 @@ needs_pd_load_pre(struct intel_engine_cs *engine, struct intel_context *to)
}
static bool
-needs_pd_load_post(struct intel_engine_cs *engine, struct intel_context *to,
- u32 hw_flags)
+needs_pd_load_post(struct intel_context *to, u32 hw_flags)
{
- struct drm_i915_private *dev_priv = engine->dev->dev_private;
-
if (!to->ppgtt)
return false;
- if (!IS_GEN8(engine->dev))
- return false;
-
- if (engine != &dev_priv->engine[RCS])
+ if (!IS_GEN8(to->i915))
return false;
if (hw_flags & MI_RESTORE_INHIBIT)
@@ -667,12 +662,11 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
{
struct intel_context *to = req->ctx;
struct intel_engine_cs *engine = req->engine;
- struct intel_context *from = engine->last_context;
- u32 hw_flags = 0;
- bool uninitialized = false;
+ struct intel_context *from;
+ u32 hw_flags;
int ret, i;
- if (skip_rcs_switch(engine, from, to))
+ if (skip_rcs_switch(engine->last_context, to))
return 0;
/* Trying to pin first makes error handling easier. */
@@ -686,9 +680,23 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
* Pin can switch back to the default context if we end up calling into
* evict_everything - as a last ditch gtt defrag effort that also
* switches to the default context. Hence we need to reload from here.
+ *
+ * XXX: Doing so is painfully broken!
*/
from = engine->last_context;
+ /*
+ * Clear this page out of any CPU caches for coherent swap-in/out. Note
+ * that thanks to write = false in this call and us not setting any gpu
+ * write domains when putting a context object onto the active list
+ * (when switching away from it), this won't block.
+ *
+ * XXX: We need a real interface to do this instead of trickery.
+ */
+ ret = i915_gem_object_set_to_gtt_domain(to->legacy_hw_ctx.rcs_state, false);
+ if (ret)
+ goto unpin_out;
+
if (needs_pd_load_pre(engine, to)) {
/* Older GENs and non render rings still want the load first,
* "PP_DCLV followed by PP_DIR_BASE register through Load
@@ -700,70 +708,36 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
goto unpin_out;
/* Doing a PD load always reloads the page dirs */
- to->ppgtt->pd_dirty_rings &= ~intel_engine_flag(engine);
+ to->ppgtt->pd_dirty_rings &= ~(1 << RCS);
}
- /*
- * Clear this page out of any CPU caches for coherent swap-in/out. Note
- * that thanks to write = false in this call and us not setting any gpu
- * write domains when putting a context object onto the active list
- * (when switching away from it), this won't block.
- *
- * XXX: We need a real interface to do this instead of trickery.
- */
- ret = i915_gem_object_set_to_gtt_domain(to->legacy_hw_ctx.rcs_state, false);
- if (ret)
- goto unpin_out;
-
- if (!to->legacy_hw_ctx.initialized || i915_gem_context_is_default(to)) {
- hw_flags |= MI_RESTORE_INHIBIT;
+ if (!to->legacy_hw_ctx.initialized || i915_gem_context_is_default(to))
/* NB: If we inhibit the restore, the context is not allowed to
* die because future work may end up depending on valid address
* space. This means we must enforce that a page table load
* occur when this occurs. */
- } else if (to->ppgtt &&
- (intel_engine_flag(engine) & to->ppgtt->pd_dirty_rings)) {
- hw_flags |= MI_FORCE_RESTORE;
- to->ppgtt->pd_dirty_rings &= ~intel_engine_flag(engine);
- }
+ hw_flags = MI_RESTORE_INHIBIT;
+ else if (to->ppgtt && to->ppgtt->pd_dirty_rings & (1 << RCS))
+ hw_flags = MI_FORCE_RESTORE;
+ else
+ hw_flags = 0;
/* We should never emit switch_mm more than once */
WARN_ON(needs_pd_load_pre(engine, to) &&
- needs_pd_load_post(engine, to, hw_flags));
-
- ret = mi_set_context(req, hw_flags);
- if (ret)
- goto unpin_out;
+ needs_pd_load_post(to, hw_flags));
- /* GEN8 does *not* require an explicit reload if the PDPs have been
- * setup, and we do not wish to move them.
- */
- if (needs_pd_load_post(engine, to, hw_flags)) {
- trace_switch_mm(engine, to);
- ret = to->ppgtt->switch_mm(to->ppgtt, req);
- /* The hardware context switch is emitted, but we haven't
- * actually changed the state - so it's probably safe to bail
- * here. Still, let the user know something dangerous has
- * happened.
- */
+ if (to != from || (hw_flags & MI_FORCE_RESTORE)) {
+ ret = mi_set_context(req, hw_flags);
if (ret) {
- DRM_ERROR("Failed to change address space on context switch\n");
+ /* Force the reload of this and the previous mm */
+ if (needs_pd_load_pre(engine, to))
+ to->ppgtt->pd_dirty_rings |= 1 << RCS;
+ if (from && needs_pd_load_pre(engine, from))
+ from->ppgtt->pd_dirty_rings |= 1 << RCS;
goto unpin_out;
}
}
- for (i = 0; i < MAX_L3_SLICES; i++) {
- if (!(to->remap_slice & (1<<i)))
- continue;
-
- ret = i915_gem_l3_remap(req, i);
- /* If it failed, try again next round */
- if (ret)
- DRM_DEBUG_DRIVER("L3 remapping failed\n");
- else
- to->remap_slice &= ~(1<<i);
- }
-
/* The backing object for the context is done after switching to the
* *next* context. Therefore we cannot retire the previous context until
* the next context has already started running. In fact, the below code
@@ -786,19 +760,46 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
i915_gem_object_ggtt_unpin(from->legacy_hw_ctx.rcs_state);
i915_gem_context_unreference(from);
}
-
- uninitialized = !to->legacy_hw_ctx.initialized;
- to->legacy_hw_ctx.initialized = true;
-
i915_gem_context_reference(to);
engine->last_context = to;
- if (uninitialized) {
+ /* GEN8 does *not* require an explicit reload if the PDPs have been
+ * setup, and we do not wish to move them.
+ */
+ if (needs_pd_load_post(to, hw_flags)) {
+ trace_switch_mm(engine, to);
+ ret = to->ppgtt->switch_mm(to->ppgtt, req);
+ /* The hardware context switch is emitted, but we haven't
+ * actually changed the state - so it's probably safe to bail
+ * here. Still, let the user know something dangerous has
+ * happened.
+ */
+ if (ret)
+ return ret;
+
+ to->ppgtt->pd_dirty_rings &= ~(1 << RCS);
+ }
+ if (hw_flags & MI_FORCE_RESTORE)
+ to->ppgtt->pd_dirty_rings &= ~(1 << RCS);
+
+ for (i = 0; i < MAX_L3_SLICES; i++) {
+ if (!(to->remap_slice & (1<<i)))
+ continue;
+
+ ret = i915_gem_l3_remap(req, i);
+ if (ret)
+ return ret;
+
+ to->remap_slice &= ~(1<<i);
+ }
+
+ if (!to->legacy_hw_ctx.initialized) {
if (engine->init_context) {
ret = engine->init_context(req);
if (ret)
- DRM_ERROR("ring init context: %d\n", ret);
+ return ret;
}
+ to->legacy_hw_ctx.initialized = true;
}
return 0;
--
2.8.0.rc3
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