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Commit 3943875e authored by Thomas Hellstrom's avatar Thomas Hellstrom
Browse files

drm/ttm: Fix vma page_prot bit manipulation 



Fix a long-standing TTM issue where we manipulated the vma page_prot
bits while mmap_sem was taken in read mode only. We now make a local
copy of the vma structure which we pass when we set the ptes.

Signed-off-by: default avatarThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: default avatarJerome Glisse <jglisse@redhat.com>
parent 59c8e663

drivers/gpu/drm/ttm/ttm_bo_vm.c

+13 −17
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 
	int retval = VM_FAULT_NOPAGE;

	struct ttm_mem_type_manager *man =

		&bdev->man[bo->mem.mem_type];

	struct vm_area_struct cvma;



	/*

	 * Work around locking order reversal in fault / nopfn
@@ -164,26 +165,21 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 
	}



	/*

	 * Strictly, we're not allowed to modify vma->vm_page_prot here,

	 * since the mmap_sem is only held in read mode. However, we

	 * modify only the caching bits of vma->vm_page_prot and

	 * consider those bits protected by

	 * the bo->mutex, as we should be the only writers.

	 * There shouldn't really be any readers of these bits except

	 * within vm_insert_mixed()? fork?

	 *

	 * TODO: Add a list of vmas to the bo, and change the

	 * vma->vm_page_prot when the object changes caching policy, with

	 * the correct locks held.

	 * Make a local vma copy to modify the page_prot member

	 * and vm_flags if necessary. The vma parameter is protected

	 * by mmap_sem in write mode.

	 */

	cvma = *vma;

	cvma.vm_page_prot = vm_get_page_prot(cvma.vm_flags);



	if (bo->mem.bus.is_iomem) {

		vma->vm_page_prot = ttm_io_prot(bo->mem.placement,

						vma->vm_page_prot);

		cvma.vm_page_prot = ttm_io_prot(bo->mem.placement,

						cvma.vm_page_prot);

	} else {

		ttm = bo->ttm;

		vma->vm_page_prot = (bo->mem.placement & TTM_PL_FLAG_CACHED) ?

		    vm_get_page_prot(vma->vm_flags) :

		    ttm_io_prot(bo->mem.placement, vma->vm_page_prot);

		if (!(bo->mem.placement & TTM_PL_FLAG_CACHED))

			cvma.vm_page_prot = ttm_io_prot(bo->mem.placement,

							cvma.vm_page_prot);



		/* Allocate all page at once, most common usage */

		if (ttm->bdev->driver->ttm_tt_populate(ttm)) {
@@ -210,7 +206,7 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 
			pfn = page_to_pfn(page);

		}



		ret = vm_insert_mixed(vma, address, pfn);

		ret = vm_insert_mixed(&cvma, address, pfn);

		/*

		 * Somebody beat us to this PTE or prefaulting to

		 * an already populated PTE, or prefaulting error.