Am 18.01.21 um 22:01 schrieb Andrey Grodzovsky:
On device removal reroute all CPU mappings to dummy page.
v3:
Remove loop to find DRM file and instead access it
by vma->vm_file->private_data. Move dummy page installation
into a separate function.
v4:
Map the entire BOs VA space into on demand allocated dummy page
on the first fault for that BO.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 82 ++++++++++++++++++++++++++++++++++++++++-
include/drm/ttm/ttm_bo_api.h | 2 +
2 files changed, 83 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 6dc96cf..ed89da3 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -34,6 +34,8 @@
#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_managed.h>
#include <linux/mm.h>
#include <linux/pfn_t.h>
#include <linux/rbtree.h>
@@ -380,25 +382,103 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
}
EXPORT_SYMBOL(ttm_bo_vm_fault_reserved);
+static void ttm_bo_release_dummy_page(struct drm_device *dev, void *res)
+{
+ struct page *dummy_page = (struct page *)res;
+
+ __free_page(dummy_page);
+}
+
+vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct ttm_buffer_object *bo = vma->vm_private_data;
+ struct ttm_bo_device *bdev = bo->bdev;
+ struct drm_device *ddev = bo->base.dev;
+ vm_fault_t ret = VM_FAULT_NOPAGE;
+ unsigned long address = vma->vm_start;
+ unsigned long num_prefault = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+ unsigned long pfn;
+ struct page *page;
+ int i;
+
+ /*
+ * Wait for buffer data in transit, due to a pipelined
+ * move.
+ */
+ ret = ttm_bo_vm_fault_idle(bo, vmf);
+ if (unlikely(ret != 0))
+ return ret;
This is superfluous and probably quite harmful here because we wait for
the hardware to do something.
We map a dummy page instead of the real BO content to the whole range
anyway, so no need to wait for the real BO content to show up.
+
+ /* Allocate new dummy page to map all the VA range in this VMA to it*/
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ return VM_FAULT_OOM;
+
+ pfn = page_to_pfn(page);
+
+ /*
+ * Prefault the entire VMA range right away to avoid further faults
+ */
+ for (i = 0; i < num_prefault; ++i) {
Maybe rename the variable to num_pages. I was confused for a moment why
we still prefault.
Alternative you can just drop i and do "for (addr = vma->vm_start; addr
< vma->vm_end; addr += PAGE_SIZE)".
+
+ if (unlikely(address >= vma->vm_end))
+ break;
+
+ if (vma->vm_flags & VM_MIXEDMAP)
+ ret = vmf_insert_mixed_prot(vma, address,
+ __pfn_to_pfn_t(pfn, PFN_DEV),
+ prot);
+ else
+ ret = vmf_insert_pfn_prot(vma, address, pfn, prot);
+
+ /* Never error on prefaulted PTEs */
+ if (unlikely((ret & VM_FAULT_ERROR))) {
+ if (i == 0)
+ return VM_FAULT_NOPAGE;
+ else
+ break;
This should probably be modified to either always return the error or
always ignore it.
Apart from that looks good to me.
Christian.
+ }
+
+ address += PAGE_SIZE;
+ }
+
+ /* Set the page to be freed using drmm release action */
+ if (drmm_add_action_or_reset(ddev, ttm_bo_release_dummy_page, page))
+ return VM_FAULT_OOM;
+
+ return ret;
+}
+EXPORT_SYMBOL(ttm_bo_vm_dummy_page);
+
vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
pgprot_t prot;
struct ttm_buffer_object *bo = vma->vm_private_data;
+ struct drm_device *ddev = bo->base.dev;
vm_fault_t ret;
+ int idx;
ret = ttm_bo_vm_reserve(bo, vmf);
if (ret)
return ret;
prot = vma->vm_page_prot;
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT, 1);
+ if (drm_dev_enter(ddev, &idx)) {
+ ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT, 1);
+ drm_dev_exit(idx);
+ } else {
+ ret = ttm_bo_vm_dummy_page(vmf, prot);
+ }
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
return ret;
dma_resv_unlock(bo->base.resv);
return ret;
+
+ return ret;
}
EXPORT_SYMBOL(ttm_bo_vm_fault);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index e17be32..12fb240 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -643,4 +643,6 @@ void ttm_bo_vm_close(struct vm_area_struct *vma);
int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write);
+vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot);
+
#endif
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