Messages in this thread Patch in this message | | | Date | Wed, 17 Apr 2019 14:48:17 -0600 | From | dann frazier <> | Subject | [RFC] arm64: swiotlb: cma_alloc error spew |
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hey, I'm seeing an issue on a couple of arm64 systems[*] where they spew ~10K "cma: cma_alloc: alloc failed" messages at boot. The errors are non-fatal, and bumping up cma to a large enough size (~128M) gets rid of them - but that seems suboptimal. Bisection shows that this started after commit fafadcd16595 ("swiotlb: don't dip into swiotlb pool for coherent allocations"). It looks like __dma_direct_alloc_pages() is opportunistically using CMA memory but falls back to non-CMA if CMA disabled or unavailable. I've demonstrated that this fallback is indeed returning a valid pointer. So perhaps the issue is really just the warning emission.
The following naive patch solves the problem for me - just silence the cma errors, since it looks like a soft error. But is there a better approach?
[*] APM X-Gene & HiSilicon Hi1620 w/ SMMU disabled
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 6310ad01f915b..0324aa606c173 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -112,7 +112,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size, /* CMA can be used only in the context which permits sleeping */ if (gfpflags_allow_blocking(gfp)) { page = dma_alloc_from_contiguous(dev, count, page_order, - gfp & __GFP_NOWARN); + true); if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { dma_release_from_contiguous(dev, page, count); page = NULL;
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