linux-kernel - [PATCH] dma-direct: reject highmem pages from dma_alloc_from

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Message-Id: <20181014181447.22783-1-hch@lst.de>
Date:   Sun, 14 Oct 2018 20:14:47 +0200
From:   Christoph Hellwig <hch@....de>
To:     iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] dma-direct: reject highmem pages from dma_alloc_from_contiguous

dma_alloc_from_contiguous can return highmem pages depending on the
setup, which a plain non-remapping DMA allocator can't handle.  Detect
this case and try the normal page allocator instead.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 kernel/dma/direct.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 87a6bc2a96c0..46fbaa49125b 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -126,6 +126,18 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 	if (gfpflags_allow_blocking(gfp)) {
 		page = dma_alloc_from_contiguous(dev, count, page_order,
 						 gfp & __GFP_NOWARN);
+		if (page && PageHighMem(page)) {
+			/*
+			 * Depending on the cma= arguments and per-arch setup
+			 * dma_alloc_from_contiguous could return highmem
+			 * pages.  Without remapping there is no way to return
+			 * them here, so log an error and fail.
+			 */
+			dev_info(dev, "Ignoring highmem page from CMA.\n");
+			dma_release_from_contiguous(dev, page, count);
+			page = NULL;
+		}
+
 		if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
 			dma_release_from_contiguous(dev, page, count);
 			page = NULL;
-- 
2.19.1