Re: [PATCH 08/17] drm/i915: Don't look at pg_dirty_rings for aliasing ppgtt

Chris Wilson
2015-04-14T17:53:48Z

On Tue, Apr 14, 2015 at 07:11:25PM +0200, Daniel Vetter wrote:
> On Tue, Apr 14, 2015 at 05:06:36PM +0100, Chris Wilson wrote:
> > On Tue, Apr 14, 2015 at 05:35:18PM +0200, Daniel Vetter wrote:
> > > We load the ppgtt ptes once per gpu reset/driver load/resume and
> > > that's all that's needed. Note that this only blows up when we're
> > > using the allocate_va_range funcs and not the special-purpose ones
> > > used. With this change we can get rid of that duplication.
> >
> > Honestly, I would prefer the test to be rewritten so that the
> > information on which vm was being used was passed along and not that
> > magic sprinkled in the middle of nowhere. e.g. execbuffer knows exactly
> > what vm it bound the objects into, and yet towards the end we decide to
> > guess again. Also, I would rather the execbuffer test be moved to
> > i915_gem_context since it is scattering internal knowledge about.
>
> Yeah I agree that there's more room for cleanup. I've done this minimal
> patch purely to shut up the bogus WARN_ONs when I tried to unify the
> gen6/7 pt alloc code in the next patch. Since it's bogus.

How about:

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index ed9232126644..be0f475ee1e5 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -638,22 +638,14 @@ mi_set_context(struct intel_engine_cs *ring,

static inline bool should_skip_switch(struct intel_engine_cs *ring,
struct intel_context *from,
- struct intel_context *to)
+ struct intel_context *to,
+ struct i915_hw_ppgtt *ppgtt)
{
- struct drm_i915_private *dev_priv = ring->dev->dev_private;
-
if (to->remap_slice)
return false;

- if (to->ppgtt) {
- if (from == to && !test_bit(ring->id,
- &to->ppgtt->pd_dirty_rings))
- return true;
- } else if (dev_priv->mm.aliasing_ppgtt) {
- if (from == to && !test_bit(ring->id,
- &dev_priv->mm.aliasing_ppgtt->pd_dirty_rings))
- return true;
- }
+ if (from == to && !test_bit(ring->id, &ppgtt->pd_dirty_rings))
+ return true;

return false;
}
@@ -661,15 +653,13 @@ static inline bool should_skip_switch(struct intel_engine_cs *ring,
static bool
needs_pd_load_pre(struct intel_engine_cs *ring, struct intel_context *to)
{
- struct drm_i915_private *dev_priv = ring->dev->dev_private;
-
if (!to->ppgtt)
return false;

if (INTEL_INFO(ring->dev)->gen < 8)
return true;

- if (ring != &dev_priv->ring[RCS])
+ if (ring->id != RCS)
return true;

return false;
@@ -679,15 +669,13 @@ static bool
needs_pd_load_post(struct intel_engine_cs *ring, struct intel_context *to,
u32 hw_flags)
{
- struct drm_i915_private *dev_priv = ring->dev->dev_private;
-
if (!to->ppgtt)
return false;

if (!IS_GEN8(ring->dev))
return false;

- if (ring != &dev_priv->ring[RCS])
+ if (ring->id != RCS)
return false;

if (hw_flags & MI_RESTORE_INHIBIT)
@@ -701,14 +689,15 @@ static int do_switch(struct intel_engine_cs *ring,
{
struct drm_i915_private *dev_priv = ring->dev->dev_private;
struct intel_context *from = ring->last_context;
+ struct i915_hw_ppgtt *ppgtt = to->ppgtt ?: dev_priv->mm.aliasing_ppgtt;
u32 hw_flags = 0;
bool uninitialized = false;
int ret, i;

- if (from != NULL && ring == &dev_priv->ring[RCS])
+ if (from != NULL && ring->id == RCS)
BUG_ON(from->legacy_hw_ctx.rcs_vma == NULL);

- if (should_skip_switch(ring, from, to))
+ if (should_skip_switch(ring, from, to, ppgtt))
return 0;

/* Trying to pin first makes error handling easier. */
@@ -851,6 +840,9 @@ done:
i915_gem_context_reference(to);
ring->last_context = to;

+ WARN(ppgtt->pd_dirty_rings & (1<<ring->id),
+ "%s didn't clear reload\n", ring->name);
+
if (uninitialized) {
if (ring->init_context) {
ret = ring->init_context(ring, to);
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index ef644e7eaac0..595daecb3283 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1385,13 +1385,6 @@ i915_gem_ringbuffer_submission(struct drm_device *dev, struct drm_file *file,
if (ret)
goto error;

- if (ctx->ppgtt)
- WARN(ctx->ppgtt->pd_dirty_rings & (1<<ring->id),
- "%s didn't clear reload\n", ring->name);
- else if (dev_priv->mm.aliasing_ppgtt)
- WARN(dev_priv->mm.aliasing_ppgtt->pd_dirty_rings &
- (1<<ring->id), "%s didn't clear reload\n", ring->name);
-
instp_mode = args->flags & I915_EXEC_CONSTANTS_MASK;
instp_mask = I915_EXEC_CONSTANTS_MASK;
switch (instp_mode) {

It gets rid of the internal knowledge of address spaces from the execbuf
code, and keeps the symmetry between handling aliasing_ppgtt and
full_ppgtt. (The former should just be a degenerate case where the PD
are all preloaded).
-Chris

--
Chris Wilson, Intel Open Source Technology Centre