On 6/22/20 5:41 AM, Daniel Vetter wrote:
On Sun, Jun 21, 2020 at 02:03:02AM -0400, Andrey Grodzovsky wrote:
On device removal reroute all CPU mappings to dummy page per drm_file
instance or imported GEM object.
Signed-off-by: Andrey Grodzovsky <andrey.grodzov...@amd.com>
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 65 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 57 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 389128b..2f8bf5e 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -35,6 +35,8 @@
#include <drm/ttm/ttm_bo_driver.h>
#include <drm/ttm/ttm_placement.h>
#include <drm/drm_vma_manager.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_file.h>
#include <linux/mm.h>
#include <linux/pfn_t.h>
#include <linux/rbtree.h>
@@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
Hm I think diff and code flow look a bit bad now. What about renaming the
current function to __ttm_bo_vm_fault and then having something like the
below:
ttm_bo_vm_fault(args) {
if (drm_dev_enter()) {
__ttm_bo_vm_fault(args);
drm_dev_exit();
} else {
drm_gem_insert_dummy_pfn();
}
}
I think drm_gem_insert_dummy_pfn(); should be portable across drivers, so
another nice point to try to unifiy drivers as much as possible.
-Daniel
pgprot_t prot;
struct ttm_buffer_object *bo = vma->vm_private_data;
vm_fault_t ret;
+ int idx;
+ struct drm_device *ddev = bo->base.dev;
- ret = ttm_bo_vm_reserve(bo, vmf);
- if (ret)
- return ret;
+ if (drm_dev_enter(ddev, &idx)) {
+ ret = ttm_bo_vm_reserve(bo, vmf);
+ if (ret)
+ goto exit;
+
+ prot = vma->vm_page_prot;
- prot = vma->vm_page_prot;
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
- if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+ ret = ttm_bo_vm_fault_reserved(vmf, prot,
TTM_BO_VM_NUM_PREFAULT);
+ if (ret == VM_FAULT_RETRY && !(vmf->flags &
FAULT_FLAG_RETRY_NOWAIT))
+ goto exit;
+
+ dma_resv_unlock(bo->base.resv);
+
+exit:
+ drm_dev_exit(idx);
return ret;
+ } else {
- dma_resv_unlock(bo->base.resv);
+ struct drm_file *file = NULL;
+ struct page *dummy_page = NULL;
+ int handle;
- return ret;
+ /* We are faulting on imported BO from dma_buf */
+ if (bo->base.dma_buf && bo->base.import_attach) {
+ dummy_page = bo->base.dummy_page;
+ /* We are faulting on non imported BO, find drm_file owning the
BO*/
Uh, we can't fish that out of the vma->vm_file pointer somehow? Or is that
one all wrong? Doing this kind of list walk looks pretty horrible.
If the vma doesn't have the right pointer I guess next option is that we
store the drm_file page in gem_bo->dummy_page, and replace it on first
export. But that's going to be tricky to track ...
For this one I hope to make all of this obsolete if Christian's suggestion from
path 1/8 about mapping
global RO dummy page for read and COW on write will be possible to implement
(testing
that indeed no memory usage explodes)
Andrey
+ } else {
+ struct drm_gem_object *gobj;
+
+ mutex_lock(&ddev->filelist_mutex);
+ list_for_each_entry(file, &ddev->filelist, lhead) {
+ spin_lock(&file->table_lock);
+ idr_for_each_entry(&file->object_idr, gobj,
handle) {
+ if (gobj == &bo->base) {
+ dummy_page = file->dummy_page;
+ break;
+ }
+ }
+ spin_unlock(&file->table_lock);
+ }
+ mutex_unlock(&ddev->filelist_mutex);
+ }
+
+ if (dummy_page) {
+ /*
+ * Let do_fault complete the PTE install e.t.c using
vmf->page
+ *
+ * TODO - should i call free_page somewhere ?
Nah, instead don't call get_page. The page will be around as long as
there's a reference for the drm_file or gem_bo, which is longer than any
mmap. Otherwise yes this would like really badly.
+ */
+ get_page(dummy_page);
+ vmf->page = dummy_page;
+ return 0;
+ } else {
+ return VM_FAULT_SIGSEGV;
Hm that would be a kernel bug, wouldn't it? WARN_ON() required here imo.
-Daniel
+ }
+ }
}
EXPORT_SYMBOL(ttm_bo_vm_fault);
--
2.7.4
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