drm/i915: Introduce DRM_I915_GEM_MMAP_OFFSET

This is really just an alias of mmap_gtt. The 'mmap offset' nomenclature
comes from the value returned by this ioctl which is the offset into the
device fd which userpace uses with mmap(2).

mmap_gtt was our initial mmap_offset implementation, this extends
our CPU mmap support to allow additional fault handlers that depends on
the object's backing pages.

Note that we multiplex mmap_gtt and mmap_offset through the same ioctl,
and use the zero extending behaviour of drm to differentiate between
them, when we inspect the flags.

To support multiple mmap types on an object we need to support multiple
mmap_offsets for an object (each offset in the global device address
space corresponding to a unique instance of the object for a file + mmap
type). As we drop the simplified drm core idea of a single mmap_offset,
we need to provide replacement hooks for the dumb mmap interface as
well.

Link: https://gitlab.freedesktop.org/mesa/mesa/merge_requests/1675
Testcase: igt/gem_mmap_offset
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191204120032.3682839-1-chris@chris-wilson.co.uk

1 files changed, 370 insertions, 91 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index d60973603cc1..37aabbfa869a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -5,6 +5,7 @@
  */
 
 #include <linux/mman.h>
+#include <linux/pfn_t.h>
 #include <linux/sizes.h>
 
 #include "gt/intel_gt.h"
@@ -14,6 +15,7 @@
 #include "i915_gem_gtt.h"
 #include "i915_gem_ioctls.h"
 #include "i915_gem_object.h"
+#include "i915_gem_mman.h"
 #include "i915_trace.h"
 #include "i915_vma.h"
 
@@ -144,6 +146,9 @@ static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)
  * 3 - Remove implicit set-domain(GTT) and synchronisation on initial
  *     pagefault; swapin remains transparent.
  *
+ * 4 - Support multiple fault handlers per object depending on object's
+ *     backing storage (a.k.a. MMAP_OFFSET).
+ *
  * Restrictions:
  *
  *  * snoopable objects cannot be accessed via the GTT. It can cause machine
@@ -171,7 +176,7 @@ static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)
  */
 int i915_gem_mmap_gtt_version(void)
 {
-	return 3;
+	return 4;
 }
 
 static inline struct i915_ggtt_view
@@ -197,29 +202,83 @@ compute_partial_view(const struct drm_i915_gem_object *obj,
 	return view;
 }
 
-/**
- * i915_gem_fault - fault a page into the GTT
- * @vmf: fault info
- *
- * The fault handler is set up by drm_gem_mmap() when a object is GTT mapped
- * from userspace.  The fault handler takes care of binding the object to
- * the GTT (if needed), allocating and programming a fence register (again,
- * only if needed based on whether the old reg is still valid or the object
- * is tiled) and inserting a new PTE into the faulting process.
- *
- * Note that the faulting process may involve evicting existing objects
- * from the GTT and/or fence registers to make room.  So performance may
- * suffer if the GTT working set is large or there are few fence registers
- * left.
- *
- * The current feature set supported by i915_gem_fault() and thus GTT mmaps
- * is exposed via I915_PARAM_MMAP_GTT_VERSION (see i915_gem_mmap_gtt_version).
- */
-vm_fault_t i915_gem_fault(struct vm_fault *vmf)
+static vm_fault_t i915_error_to_vmf_fault(int err)
+{
+	switch (err) {
+	default:
+		WARN_ONCE(err, "unhandled error in %s: %i\n", __func__, err);
+		/* fallthrough */
+	case -EIO: /* shmemfs failure from swap device */
+	case -EFAULT: /* purged object */
+	case -ENODEV: /* bad object, how did you get here! */
+		return VM_FAULT_SIGBUS;
+
+	case -ENOSPC: /* shmemfs allocation failure */
+	case -ENOMEM: /* our allocation failure */
+		return VM_FAULT_OOM;
+
+	case 0:
+	case -EAGAIN:
+	case -ERESTARTSYS:
+	case -EINTR:
+	case -EBUSY:
+		/*
+		 * EBUSY is ok: this just means that another thread
+		 * already did the job.
+		 */
+		return VM_FAULT_NOPAGE;
+	}
+}
+
+static vm_fault_t vm_fault_cpu(struct vm_fault *vmf)
+{
+	struct vm_area_struct *area = vmf->vma;
+	struct i915_mmap_offset *mmo = area->vm_private_data;
+	struct drm_i915_gem_object *obj = mmo->obj;
+	unsigned long i, size = area->vm_end - area->vm_start;
+	bool write = area->vm_flags & VM_WRITE;
+	vm_fault_t ret = VM_FAULT_SIGBUS;
+	int err;
+
+	if (!i915_gem_object_has_struct_page(obj))
+		return ret;
+
+	/* Sanity check that we allow writing into this object */
+	if (i915_gem_object_is_readonly(obj) && write)
+		return ret;
+
+	err = i915_gem_object_pin_pages(obj);
+	if (err)
+		return i915_error_to_vmf_fault(err);
+
+	/* PTEs are revoked in obj->ops->put_pages() */
+	for (i = 0; i < size >> PAGE_SHIFT; i++) {
+		struct page *page = i915_gem_object_get_page(obj, i);
+
+		ret = vmf_insert_pfn(area,
+				     (unsigned long)area->vm_start + i * PAGE_SIZE,
+				     page_to_pfn(page));
+		if (ret != VM_FAULT_NOPAGE)
+			break;
+	}
+
+	if (write) {
+		GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
+		obj->cache_dirty = true; /* XXX flush after PAT update? */
+		obj->mm.dirty = true;
+	}
+
+	i915_gem_object_unpin_pages(obj);
+
+	return ret;
+}
+
+static vm_fault_t vm_fault_gtt(struct vm_fault *vmf)
 {
 #define MIN_CHUNK_PAGES (SZ_1M >> PAGE_SHIFT)
 	struct vm_area_struct *area = vmf->vma;
-	struct drm_i915_gem_object *obj = to_intel_bo(area->vm_private_data);
+	struct i915_mmap_offset *mmo = area->vm_private_data;
+	struct drm_i915_gem_object *obj = mmo->obj;
 	struct drm_device *dev = obj->base.dev;
 	struct drm_i915_private *i915 = to_i915(dev);
 	struct intel_runtime_pm *rpm = &i915->runtime_pm;
@@ -312,6 +371,9 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 		list_add(&obj->userfault_link, &i915->ggtt.userfault_list);
 	mutex_unlock(&i915->ggtt.vm.mutex);
 
+	/* Track the mmo associated with the fenced vma */
+	vma->mmo = mmo;
+
 	if (IS_ACTIVE(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND))
 		intel_wakeref_auto(&i915->ggtt.userfault_wakeref,
 				   msecs_to_jiffies_timeout(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND));
@@ -332,67 +394,36 @@ err_rpm:
 	intel_runtime_pm_put(rpm, wakeref);
 	i915_gem_object_unpin_pages(obj);
 err:
-	switch (ret) {
-	default:
-		WARN_ONCE(ret, "unhandled error in %s: %i\n", __func__, ret);
-		/* fallthrough */
-	case -EIO: /* shmemfs failure from swap device */
-	case -EFAULT: /* purged object */
-	case -ENODEV: /* bad object, how did you get here! */
-		return VM_FAULT_SIGBUS;
-
-	case -ENOSPC: /* shmemfs allocation failure */
-	case -ENOMEM: /* our allocation failure */
-		return VM_FAULT_OOM;
-
-	case 0:
-	case -EAGAIN:
-	case -ERESTARTSYS:
-	case -EINTR:
-	case -EBUSY:
-		/*
-		 * EBUSY is ok: this just means that another thread
-		 * already did the job.
-		 */
-		return VM_FAULT_NOPAGE;
-	}
+	return i915_error_to_vmf_fault(ret);
 }
 
-void __i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
+void __i915_gem_object_release_mmap_gtt(struct drm_i915_gem_object *obj)
 {
 	struct i915_vma *vma;
 
 	GEM_BUG_ON(!obj->userfault_count);
 
-	obj->userfault_count = 0;
-	list_del(&obj->userfault_link);
-	drm_vma_node_unmap(&obj->base.vma_node,
-			   obj->base.dev->anon_inode->i_mapping);
-
 	for_each_ggtt_vma(vma, obj)
-		i915_vma_unset_userfault(vma);
+		i915_vma_revoke_mmap(vma);
+
+	GEM_BUG_ON(obj->userfault_count);
 }
 
-/**
- * i915_gem_object_release_mmap - remove physical page mappings
- * @obj: obj in question
- *
- * Preserve the reservation of the mmapping with the DRM core code, but
- * relinquish ownership of the pages back to the system.
- *
+/*
  * It is vital that we remove the page mapping if we have mapped a tiled
  * object through the GTT and then lose the fence register due to
  * resource pressure. Similarly if the object has been moved out of the
  * aperture, than pages mapped into userspace must be revoked. Removing the
  * mapping will then trigger a page fault on the next user access, allowing
- * fixup by i915_gem_fault().
+ * fixup by vm_fault_gtt().
  */
-void i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
+static void i915_gem_object_release_mmap_gtt(struct drm_i915_gem_object *obj)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 	intel_wakeref_t wakeref;
 
-	/* Serialisation between user GTT access and our code depends upon
+	/*
+	 * 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.
 	 *
@@ -406,9 +437,10 @@ void i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
 	if (!obj->userfault_count)
 		goto out;
 
-	__i915_gem_object_release_mmap(obj);
+	__i915_gem_object_release_mmap_gtt(obj);
 
-	/* Ensure that the CPU's PTE are revoked and there are not outstanding
+	/*
+	 * Ensure that the CPU's PTE are revoked and there are not outstanding
 	 * memory transactions from userspace before we return. The TLB
 	 * flushing implied above by changing the PTE above *should* be
 	 * sufficient, an extra barrier here just provides us with a bit
@@ -422,57 +454,149 @@ out:
 	intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 }
 
-static int create_mmap_offset(struct drm_i915_gem_object *obj)
+void i915_gem_object_release_mmap_offset(struct drm_i915_gem_object *obj)
+{
+	struct i915_mmap_offset *mmo;
+
+	spin_lock(&obj->mmo.lock);
+	list_for_each_entry(mmo, &obj->mmo.offsets, offset) {
+		/*
+		 * vma_node_unmap for GTT mmaps handled already in
+		 * __i915_gem_object_release_mmap_gtt
+		 */
+		if (mmo->mmap_type == I915_MMAP_TYPE_GTT)
+			continue;
+
+		spin_unlock(&obj->mmo.lock);
+		drm_vma_node_unmap(&mmo->vma_node,
+				   obj->base.dev->anon_inode->i_mapping);
+		spin_lock(&obj->mmo.lock);
+	}
+	spin_unlock(&obj->mmo.lock);
+}
+
+/**
+ * i915_gem_object_release_mmap - remove physical page mappings
+ * @obj: obj in question
+ *
+ * Preserve the reservation of the mmapping with the DRM core code, but
+ * relinquish ownership of the pages back to the system.
+ */
+void i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
+{
+	i915_gem_object_release_mmap_gtt(obj);
+	i915_gem_object_release_mmap_offset(obj);
+}
+
+static struct i915_mmap_offset *
+mmap_offset_attach(struct drm_i915_gem_object *obj,
+		   enum i915_mmap_type mmap_type,
+		   struct drm_file *file)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
-	struct intel_gt *gt = &i915->gt;
+	struct i915_mmap_offset *mmo;
 	int err;
 
-	err = drm_gem_create_mmap_offset(&obj->base);
+	mmo = kmalloc(sizeof(*mmo), GFP_KERNEL);
+	if (!mmo)
+		return ERR_PTR(-ENOMEM);
+
+	mmo->obj = obj;
+	mmo->dev = obj->base.dev;
+	mmo->file = file;
+	mmo->mmap_type = mmap_type;
+	drm_vma_node_reset(&mmo->vma_node);
+
+	err = drm_vma_offset_add(mmo->dev->vma_offset_manager, &mmo->vma_node,
+				 obj->base.size / PAGE_SIZE);
 	if (likely(!err))
-		return 0;
+		goto out;
 
 	/* Attempt to reap some mmap space from dead objects */
-	err = intel_gt_retire_requests_timeout(gt, MAX_SCHEDULE_TIMEOUT);
+	err = intel_gt_retire_requests_timeout(&i915->gt, MAX_SCHEDULE_TIMEOUT);
 	if (err)
-		return err;
+		goto err;
 
 	i915_gem_drain_freed_objects(i915);
-	return drm_gem_create_mmap_offset(&obj->base);
+	err = drm_vma_offset_add(mmo->dev->vma_offset_manager, &mmo->vma_node,
+				 obj->base.size / PAGE_SIZE);
+	if (err)
+		goto err;
+
+out:
+	if (file)
+		drm_vma_node_allow(&mmo->vma_node, file);
+
+	spin_lock(&obj->mmo.lock);
+	list_add(&mmo->offset, &obj->mmo.offsets);
+	spin_unlock(&obj->mmo.lock);
+
+	return mmo;
+
+err:
+	kfree(mmo);
+	return ERR_PTR(err);
 }
 
-int
-i915_gem_mmap_gtt(struct drm_file *file,
-		  struct drm_device *dev,
-		  u32 handle,
-		  u64 *offset)
+static int
+__assign_mmap_offset(struct drm_file *file,
+		     u32 handle,
+		     enum i915_mmap_type mmap_type,
+		     u64 *offset)
 {
 	struct drm_i915_gem_object *obj;
-	int ret;
-
-	if (!i915_ggtt_has_aperture(&to_i915(dev)->ggtt))
-		return -ENODEV;
+	struct i915_mmap_offset *mmo;
+	int err;
 
 	obj = i915_gem_object_lookup(file, handle);
 	if (!obj)
 		return -ENOENT;
 
-	if (i915_gem_object_never_bind_ggtt(obj)) {
-		ret = -ENODEV;
+	if (mmap_type == I915_MMAP_TYPE_GTT &&
+	    i915_gem_object_never_bind_ggtt(obj)) {
+		err = -ENODEV;
 		goto out;
 	}
 
-	ret = create_mmap_offset(obj);
-	if (ret == 0)
-		*offset = drm_vma_node_offset_addr(&obj->base.vma_node);
+	if (mmap_type != I915_MMAP_TYPE_GTT &&
+	    !i915_gem_object_has_struct_page(obj)) {
+		err = -ENODEV;
+		goto out;
+	}
+
+	mmo = mmap_offset_attach(obj, mmap_type, file);
+	if (IS_ERR(mmo)) {
+		err = PTR_ERR(mmo);
+		goto out;
+	}
 
+	*offset = drm_vma_node_offset_addr(&mmo->vma_node);
+	err = 0;
 out:
 	i915_gem_object_put(obj);
-	return ret;
+	return err;
+}
+
+int
+i915_gem_dumb_mmap_offset(struct drm_file *file,
+			  struct drm_device *dev,
+			  u32 handle,
+			  u64 *offset)
+{
+	enum i915_mmap_type mmap_type;
+
+	if (boot_cpu_has(X86_FEATURE_PAT))
+		mmap_type = I915_MMAP_TYPE_WC;
+	else if (!i915_ggtt_has_aperture(&to_i915(dev)->ggtt))
+		return -ENODEV;
+	else
+		mmap_type = I915_MMAP_TYPE_GTT;
+
+	return __assign_mmap_offset(file, handle, mmap_type, offset);
 }
 
 /**
- * i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
+ * i915_gem_mmap_offset_ioctl - prepare an object for GTT mmap'ing
  * @dev: DRM device
  * @data: GTT mapping ioctl data
  * @file: GEM object info
@@ -487,12 +611,167 @@ out:
  * userspace.
  */
 int
-i915_gem_mmap_gtt_ioctl(struct drm_device *dev, void *data,
-			struct drm_file *file)
+i915_gem_mmap_offset_ioctl(struct drm_device *dev, void *data,
+			   struct drm_file *file)
 {
-	struct drm_i915_gem_mmap_gtt *args = data;
+	struct drm_i915_private *i915 = to_i915(dev);
+	struct drm_i915_gem_mmap_offset *args = data;
+	enum i915_mmap_type type;
+
+	if (args->extensions)
+		return -EINVAL;
+
+	switch (args->flags) {
+	case I915_MMAP_OFFSET_GTT:
+		if (!i915_ggtt_has_aperture(&i915->ggtt))
+			return -ENODEV;
+		type = I915_MMAP_TYPE_GTT;
+		break;
+
+	case I915_MMAP_OFFSET_WC:
+		if (!boot_cpu_has(X86_FEATURE_PAT))
+			return -ENODEV;
+		type = I915_MMAP_TYPE_WC;
+		break;
+
+	case I915_MMAP_OFFSET_WB:
+		type = I915_MMAP_TYPE_WB;
+		break;
+
+	case I915_MMAP_OFFSET_UC:
+		if (!boot_cpu_has(X86_FEATURE_PAT))
+			return -ENODEV;
+		type = I915_MMAP_TYPE_UC;
+		break;
+
+	default:
+		return -EINVAL;
+	}
 
-	return i915_gem_mmap_gtt(file, dev, args->handle, &args->offset);
+	return __assign_mmap_offset(file, args->handle, type, &args->offset);
+}
+
+static void vm_open(struct vm_area_struct *vma)
+{
+	struct i915_mmap_offset *mmo = vma->vm_private_data;
+	struct drm_i915_gem_object *obj = mmo->obj;
+
+	GEM_BUG_ON(!obj);
+	i915_gem_object_get(obj);
+}
+
+static void vm_close(struct vm_area_struct *vma)
+{
+	struct i915_mmap_offset *mmo = vma->vm_private_data;
+	struct drm_i915_gem_object *obj = mmo->obj;
+
+	GEM_BUG_ON(!obj);
+	i915_gem_object_put(obj);
+}
+
+static const struct vm_operations_struct vm_ops_gtt = {
+	.fault = vm_fault_gtt,
+	.open = vm_open,
+	.close = vm_close,
+};
+
+static const struct vm_operations_struct vm_ops_cpu = {
+	.fault = vm_fault_cpu,
+	.open = vm_open,
+	.close = vm_close,
+};
+
+/*
+ * This overcomes the limitation in drm_gem_mmap's assignment of a
+ * drm_gem_object as the vma->vm_private_data. Since we need to
+ * be able to resolve multiple mmap offsets which could be tied
+ * to a single gem object.
+ */
+int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct drm_vma_offset_node *node;
+	struct drm_file *priv = filp->private_data;
+	struct drm_device *dev = priv->minor->dev;
+	struct i915_mmap_offset *mmo = NULL;
+	struct drm_gem_object *obj = NULL;
+
+	if (drm_dev_is_unplugged(dev))
+		return -ENODEV;
+
+	drm_vma_offset_lock_lookup(dev->vma_offset_manager);
+	node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
+						  vma->vm_pgoff,
+						  vma_pages(vma));
+	if (likely(node)) {
+		mmo = container_of(node, struct i915_mmap_offset,
+				   vma_node);
+		/*
+		 * In our dependency chain, the drm_vma_offset_node
+		 * depends on the validity of the mmo, which depends on
+		 * the gem object. However the only reference we have
+		 * at this point is the mmo (as the parent of the node).
+		 * Try to check if the gem object was at least cleared.
+		 */
+		if (!mmo || !mmo->obj) {
+			drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
+			return -EINVAL;
+		}
+		/*
+		 * Skip 0-refcnted objects as it is in the process of being
+		 * destroyed and will be invalid when the vma manager lock
+		 * is released.
+		 */
+		obj = &mmo->obj->base;
+		if (!kref_get_unless_zero(&obj->refcount))
+			obj = NULL;
+	}
+	drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
+	if (!obj)
+		return -EINVAL;
+
+	if (!drm_vma_node_is_allowed(node, priv)) {
+		drm_gem_object_put_unlocked(obj);
+		return -EACCES;
+	}
+
+	if (i915_gem_object_is_readonly(to_intel_bo(obj))) {
+		if (vma->vm_flags & VM_WRITE) {
+			drm_gem_object_put_unlocked(obj);
+			return -EINVAL;
+		}
+		vma->vm_flags &= ~VM_MAYWRITE;
+	}
+
+	vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
+	vma->vm_private_data = mmo;
+
+	switch (mmo->mmap_type) {
+	case I915_MMAP_TYPE_WC:
+		vma->vm_page_prot =
+			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+		vma->vm_ops = &vm_ops_cpu;
+		break;
+
+	case I915_MMAP_TYPE_WB:
+		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+		vma->vm_ops = &vm_ops_cpu;
+		break;
+
+	case I915_MMAP_TYPE_UC:
+		vma->vm_page_prot =
+			pgprot_noncached(vm_get_page_prot(vma->vm_flags));
+		vma->vm_ops = &vm_ops_cpu;
+		break;
+
+	case I915_MMAP_TYPE_GTT:
+		vma->vm_page_prot =
+			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+		vma->vm_ops = &vm_ops_gtt;
+		break;
+	}
+	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
+
+	return 0;
 }
 
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)