[Intel-gfx] [PATCH 01/41] drm/i915: Move user fault tracking to a separate list

[Chris Wilson]

We want to decouple RPM and struct_mutex, but currently RPM has to walk
the list of bound objects and remove userspace mmapping before we
suspend (otherwise userspace may continue to access the GTT whilst it is
powered down). This currently requires the struct_mutex to walk the
bound_list, but if we move that to a separate list and lock we can take
the first step towards removing the struct_mutex.

v2: Split runtime suspend unmapping vs regular unmapping, to make the
locking (and barriers) clearer. Add the object to the userfault_list
prior to inserting the first PTE, the race between add/revoke depends
upon struct_mutex for regular unmappings and rpm for runtime-suspend.

Signed-off-by: Chris Wilson 
Reviewed-by: Daniel Vetter  #v1
---
 drivers/gpu/drm/i915/i915_debugfs.c   |  2 +-
 drivers/gpu/drm/i915/i915_drv.h   | 20 +++--
 drivers/gpu/drm/i915/i915_gem.c   | 42 +++
 drivers/gpu/drm/i915/i915_gem_evict.c |  2 +-
 drivers/gpu/drm/i915/i915_gem_fence.c |  2 +-
 5 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
b/drivers/gpu/drm/i915/i915_debugfs.c
index 20638d22bbad..1b402eebd3d9 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -107,7 +107,7 @@ static char get_tiling_flag(struct drm_i915_gem_object *obj)
 
 static char get_global_flag(struct drm_i915_gem_object *obj)
 {
-   return obj->fault_mappable ? 'g' : ' ';
+   return !list_empty(>userfault_link) ? 'g' : ' ';
 }
 
 static char get_pin_mapped_flag(struct drm_i915_gem_object *obj)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5b2b7f3c6e76..489cf5201ee0 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1361,6 +1361,14 @@ struct i915_gem_mm {
 */
struct list_head unbound_list;
 
+   /** Protects access to the userfault_list */
+   spinlock_t userfault_lock;
+
+   /** List of all objects in gtt_space, currently mmaped by userspace.
+* All objects within this list must also be on bound_list.
+*/
+   struct list_head userfault_list;
+
/** Usable portion of the GTT for GEM */
unsigned long stolen_base; /* limited to low memory (32-bit) */
 
@@ -2205,6 +2213,11 @@ struct drm_i915_gem_object {
struct drm_mm_node *stolen;
struct list_head global_list;
 
+   /**
+* Whether the object is currently in the GGTT mmap.
+*/
+   struct list_head userfault_link;
+
/** Used in execbuf to temporarily hold a ref */
struct list_head obj_exec_link;
 
@@ -2232,13 +2245,6 @@ struct drm_i915_gem_object {
 */
unsigned int madv:2;
 
-   /**
-* Whether the current gtt mapping needs to be mappable (and isn't just
-* mappable by accident). Track pin and fault separate for a more
-* accurate mappable working set.
-*/
-   unsigned int fault_mappable:1;
-
/*
 * Is the object to be mapped as read-only to the GPU
 * Only honoured if hardware has relevant pte bit
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 8ed8e24025ac..b7a6bcd15bc9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1839,16 +1839,19 @@ int i915_gem_fault(struct vm_area_struct *area, struct 
vm_fault *vmf)
if (ret)
goto err_unpin;
 
+   /* Mark as being mmapped into userspace for later revocation */
+   spin_lock(_priv->mm.userfault_lock);
+   if (list_empty(>userfault_link))
+   list_add(>userfault_link, _priv->mm.userfault_list);
+   spin_unlock(_priv->mm.userfault_lock);
+
/* Finally, remap it using the new GTT offset */
ret = remap_io_mapping(area,
   area->vm_start + 
(vma->ggtt_view.params.partial.offset << PAGE_SHIFT),
   (ggtt->mappable_base + vma->node.start) >> 
PAGE_SHIFT,
   min_t(u64, vma->size, area->vm_end - 
area->vm_start),
   >mappable);
-   if (ret)
-   goto err_unpin;
 
-   obj->fault_mappable = true;
 err_unpin:
__i915_vma_unpin(vma);
 err_unlock:
@@ -1916,13 +1919,22 @@ int i915_gem_fault(struct vm_area_struct *area, struct 
vm_fault *vmf)
 void
 i915_gem_release_mmap(struct drm_i915_gem_object *obj)
 {
+   struct drm_i915_private *i915 = to_i915(obj->base.dev);
+   bool zap = false;
+
/* Serialisation between user GTT access and our code depends upon
 * revoking the CPU's PTE whilst the mutex is held. The next user
 * pagefault then has to wait until we release the mutex.
 */
-   lockdep_assert_held(>base.dev->struct_mutex);
+   lockdep_assert_held(>drm.struct_mutex);
 
-   if 

[Intel-gfx] [PATCH 01/41] drm/i915: Move user fault tracking to a separate list

[Chris Wilson]

We want to decouple RPM and struct_mutex, but currently RPM has to walk
the list of bound objects and remove userspace mmapping before we
suspend (otherwise userspace may continue to access the GTT whilst it is
powered down). This currently requires the struct_mutex to walk the
bound_list, but if we move that to a separate list and lock we can take
the first step towards removing the struct_mutex.

v2: Split runtime suspend unmapping vs regular unmapping, to make the
locking (and barriers) clearer. Add the object to the userfault_list
prior to inserting the first PTE, the race between add/revoke depends
upon struct_mutex for regular unmappings and rpm for runtime-suspend.

Signed-off-by: Chris Wilson 
Reviewed-by: Daniel Vetter  #v1
---
 drivers/gpu/drm/i915/i915_debugfs.c   |  2 +-
 drivers/gpu/drm/i915/i915_drv.h   | 20 +++--
 drivers/gpu/drm/i915/i915_gem.c   | 42 +++
 drivers/gpu/drm/i915/i915_gem_evict.c |  2 +-
 drivers/gpu/drm/i915/i915_gem_fence.c |  2 +-
 5 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
b/drivers/gpu/drm/i915/i915_debugfs.c
index 515c206ba653..c1e3bd785b71 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -107,7 +107,7 @@ static char get_tiling_flag(struct drm_i915_gem_object *obj)
 
 static char get_global_flag(struct drm_i915_gem_object *obj)
 {
-   return obj->fault_mappable ? 'g' : ' ';
+   return !list_empty(>userfault_link) ? 'g' : ' ';
 }
 
 static char get_pin_mapped_flag(struct drm_i915_gem_object *obj)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index fe875b27a6bf..8077d325aa78 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1360,6 +1360,14 @@ struct i915_gem_mm {
 */
struct list_head unbound_list;
 
+   /** Protects access to the userfault_list */
+   spinlock_t userfault_lock;
+
+   /** List of all objects in gtt_space, currently mmaped by userspace.
+* All objects within this list must also be on bound_list.
+*/
+   struct list_head userfault_list;
+
/** Usable portion of the GTT for GEM */
unsigned long stolen_base; /* limited to low memory (32-bit) */
 
@@ -2208,6 +2216,11 @@ struct drm_i915_gem_object {
struct drm_mm_node *stolen;
struct list_head global_list;
 
+   /**
+* Whether the object is currently in the GGTT mmap.
+*/
+   struct list_head userfault_link;
+
/** Used in execbuf to temporarily hold a ref */
struct list_head obj_exec_link;
 
@@ -2235,13 +2248,6 @@ struct drm_i915_gem_object {
 */
unsigned int madv:2;
 
-   /**
-* Whether the current gtt mapping needs to be mappable (and isn't just
-* mappable by accident). Track pin and fault separate for a more
-* accurate mappable working set.
-*/
-   unsigned int fault_mappable:1;
-
/*
 * Is the object to be mapped as read-only to the GPU
 * Only honoured if hardware has relevant pte bit
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fe92e28ea0a8..6da9514ceefa 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1839,16 +1839,19 @@ int i915_gem_fault(struct vm_area_struct *area, struct 
vm_fault *vmf)
if (ret)
goto err_unpin;
 
+   /* Mark as being mmapped into userspace for later revocation */
+   spin_lock(_priv->mm.userfault_lock);
+   if (list_empty(>userfault_link))
+   list_add(>userfault_link, _priv->mm.userfault_list);
+   spin_unlock(_priv->mm.userfault_lock);
+
/* Finally, remap it using the new GTT offset */
ret = remap_io_mapping(area,
   area->vm_start + 
(vma->ggtt_view.params.partial.offset << PAGE_SHIFT),
   (ggtt->mappable_base + vma->node.start) >> 
PAGE_SHIFT,
   min_t(u64, vma->size, area->vm_end - 
area->vm_start),
   >mappable);
-   if (ret)
-   goto err_unpin;
 
-   obj->fault_mappable = true;
 err_unpin:
__i915_vma_unpin(vma);
 err_unlock:
@@ -1916,13 +1919,22 @@ err:
 void
 i915_gem_release_mmap(struct drm_i915_gem_object *obj)
 {
+   struct drm_i915_private *i915 = to_i915(obj->base.dev);
+   bool zap = false;
+
/* Serialisation between user GTT access and our code depends upon
 * revoking the CPU's PTE whilst the mutex is held. The next user
 * pagefault then has to wait until we release the mutex.
 */
-   lockdep_assert_held(>base.dev->struct_mutex);
+   lockdep_assert_held(>drm.struct_mutex);
 
-   if (!obj->fault_mappable)
+   spin_lock(>mm.userfault_lock);
+   if