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[71.56.235.36]) by smtp.gmail.com with ESMTPSA id c99sm47406itd.4.2019.04.17.13.48.17 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 17 Apr 2019 13:48:18 -0700 (PDT) Date: Wed, 17 Apr 2019 14:48:17 -0600 From: dann frazier To: Christoph Hellwig Subject: [RFC] arm64: swiotlb: cma_alloc error spew Message-ID: <20190417204817.GA28897@xps13.dannf> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190417_134824_840718_495D6C00 X-CRM114-Status: GOOD ( 12.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Xinwei Kong , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Robin Murphy , linux-arm-kernel@lists.infradead.org, Marek Szyprowski Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP 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;