[PATCH] drm/ttm: dma: Don't crash on memory in the vmalloc range

[Alexandre Courbot <acourbot@nvidia.com>]

dma_alloc_coherent() can return memory in the vmalloc range.
virt_to_page() cannot handle such addresses and crashes. This
patch detects such cases and obtains the struct page * using
vmalloc_to_page() instead.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
This patch is a follow-up of the following discussion:

https://www.marc.info/?l=dri-devel&m=141579595431254&w=3

It works for me on both 32-bit and 64-bit Tegra, so I am not convinced
that Thierry's initial change from virt_to_page() to phys_to_page() is
still required - Thierry, can you confirm whether your patch is still
relevant after this one?

 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index 01e1d27eb078..3077f1554099 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -342,9 +342,12 @@ static struct dma_page *__ttm_dma_alloc_page(struct dma_pool *pool)
 	d_page->vaddr = dma_alloc_coherent(pool->dev, pool->size,
 					   &d_page->dma,
 					   pool->gfp_flags);
-	if (d_page->vaddr)
-		d_page->p = virt_to_page(d_page->vaddr);
-	else {
+	if (d_page->vaddr) {
+		if (is_vmalloc_addr(d_page->vaddr))
+			d_page->p = vmalloc_to_page(d_page->vaddr);
+		else
+			d_page->p = virt_to_page(d_page->vaddr);
+	} else {
 		kfree(d_page);
 		d_page = NULL;
 	}
-- 
2.4.0