[lkml]   [2019]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[RFC] arm64: swiotlb: cma_alloc error spew
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

[*] 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;

 \ /
  Last update: 2019-04-17 22:49    [W:0.057 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site