Commit 267d51d7 authored by Andrey Grodzovsky's avatar Andrey Grodzovsky
Browse files

drm/ttm: Remap all page faults to per process dummy page. 



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.

v5: Remove duplicate return.

v6: Polish ttm_bo_vm_dummy_page, remove superfluous code.

Signed-off-by: default avatarAndrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: default avatarChristian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210512142648.666476-2-andrey.grodzovsky@amd.com
parent e52e4a31

drivers/gpu/drm/ttm/ttm_bo_vm.c

+53 −1
Original line number Diff line number Diff line
@@ -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>
@@ -380,19 +382,69 @@ 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 drm_device *ddev = bo->base.dev;

	vm_fault_t ret = VM_FAULT_NOPAGE;

	unsigned long address;

	unsigned long pfn;

	struct page *page;



	/* 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;



	/* 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;



	pfn = page_to_pfn(page);



	/* Prefault the entire VMA range right away to avoid further faults */

	for (address = vma->vm_start; address < vma->vm_end; address += PAGE_SIZE) {



		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);

	}



	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;

	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;

include/drm/ttm/ttm_bo_api.h

+2 −0
Original line number Diff line number Diff line
@@ -620,4 +620,6 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr, 
		     void *buf, int len, int write);

bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all);



vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot);



#endif