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

Abdiel Janulgue
2019-10-23T08:25:13Z

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

v2: bail out of inserting PTEs when failing to insert the
fault address
v3: has struct page check

Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 128 ++++++++++++++++++-----
1 file changed, 103 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 db810af1cc13..1a4198971d0c 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 +201,70 @@ 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;
+
+ if (!i915_gem_object_has_struct_page(obj))
+ return VM_FAULT_SIGBUS;
+
+ /* 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 +404,7 @@ 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)
@@ -650,6 +692,33 @@ 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
@@ -717,7 +786,16 @@ 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;