[PATCH 5/5] drm/i915: Add cpu fault handler for mmap_offset

[Abdiel Janulgue]

Fault handler to handle missing pages for shmem-backed objects.

v2: bail out of inserting PTEs when failing to insert the
    fault address

Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 125 ++++++++++++++++++-----
 1 file changed, 100 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 5ee97c64c6d6..92327fa27ec8 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"
@@ -200,6 +201,67 @@ compute_partial_view(const struct drm_i915_gem_object *obj,
 	return view;
 }
 
+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 i915_gem_fault_cpu(struct vm_fault *vmf)
+{
+	struct vm_area_struct *area = vmf->vma;
+	struct i915_mmap_offset *priv = area->vm_private_data;
+	struct drm_i915_gem_object *obj = priv->obj;
+	vm_fault_t vmf_ret;
+	unsigned long i, size = area->vm_end - area->vm_start;
+	bool write = area->vm_flags & VM_WRITE;
+	int ret;
+
+	/* Sanity check that we allow writing into this object */
+	if (i915_gem_object_is_readonly(obj) && write)
+		return VM_FAULT_SIGBUS;
+
+	ret = i915_gem_object_pin_pages(obj);
+	if (ret)
+		return i915_error_to_vmf_fault(ret);
+
+	for (i = 0; i < size >> PAGE_SHIFT; i++) {
+		struct page *page = i915_gem_object_get_page(obj, i);
+
+		vmf_ret = vmf_insert_pfn(area,
+					 (unsigned long)area->vm_start + i * PAGE_SIZE,
+					 page_to_pfn(page));
+		if (vmf_ret != VM_FAULT_NOPAGE)
+			break;
+	}
+
+	i915_gem_object_unpin_pages(obj);
+
+	return vmf_ret;
+}
+
 /**
  * i915_gem_fault - fault a page into the GTT
  * @vmf: fault info
@@ -339,30 +401,7 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 	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_gtt(struct drm_i915_gem_object *obj)
@@ -647,6 +686,33 @@ static const struct vm_operations_struct i915_gem_gtt_vm_ops = {
 	.close = i915_gem_vm_close,
 };
 
+static const struct vm_operations_struct i915_gem_cpu_vm_ops = {
+	.fault = i915_gem_fault_cpu,
+	.open = i915_gem_vm_open,
+	.close = i915_gem_vm_close,
+};
+
+static void set_vmdata_mmap_offset(struct i915_mmap_offset *mmo, struct vm_area_struct *vma)
+{
+	switch (mmo->mmap_type) {
+	case I915_MMAP_TYPE_WC:
+		vma->vm_page_prot =
+			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+		break;
+	case I915_MMAP_TYPE_WB:
+		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+		break;
+	case I915_MMAP_TYPE_UC:
+		vma->vm_page_prot =
+			pgprot_noncached(vm_get_page_prot(vma->vm_flags));
+		break;
+	default:
+		break;
+	}
+
+	vma->vm_ops = &i915_gem_cpu_vm_ops;
+}
+
 /* 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
@@ -714,7 +780,16 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
 	vma->vm_private_data = mmo;
 
-	vma->vm_ops = &i915_gem_gtt_vm_ops;
+	switch (mmo->mmap_type) {
+	case I915_MMAP_TYPE_WC:
+	case I915_MMAP_TYPE_WB:
+	case I915_MMAP_TYPE_UC:
+		set_vmdata_mmap_offset(mmo, vma);
+		break;
+	case I915_MMAP_TYPE_GTT:
+		vma->vm_ops = &i915_gem_gtt_vm_ops;
+		break;
+	}
 
 	return 0;
 }
-- 
2.23.0