From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH/RFC 1/2] arm64: mm: Silently allow devices lacking IOMMU group Date: Mon, 23 Jan 2017 12:34:05 +0000 Message-ID: <66c082c6-da2e-9765-0db8-e0ba2c5bd501@arm.com> References: <148517349585.18128.10696161017872202809.sendpatchset@little-apple> <148517353630.18128.12799811817831597628.sendpatchset@little-apple> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <148517353630.18128.12799811817831597628.sendpatchset@little-apple> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Magnus Damm , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Cc: linux-renesas-soc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, horms+renesas-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org, laurent.pinchart+renesas-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, geert+renesas-gXvu3+zWzMSzQB+pC5nmwQ@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi Magnus, On 23/01/17 12:12, Magnus Damm wrote: > From: Magnus Damm > > Consider failure of iommu_get_domain_for_dev() as non-critical and > get rid of the warning printout. This allows IOMMU properties to be > included in the DTB even though the kernel is configured with > CONFIG_IOMMU_API=n or in case a particular IOMMU driver refuses to > enable IOMMU support for a certain slave device and returns error > from the ->add_device() callback. > > This is only a cosmetic change that removes console warning printouts. The warning is there for a reason - at this point, we *expected* the device to be using an IOMMU for DMA, so a failure is significant. Rather than masking genuine failures in other cases because your case deliberately breaks that expectation, simply change the expectation - i.e. rather than letting of_xlate() succeed then failing add_device() later, reject the of_xlate() call up-front such that the DMA layer never gets told about the IOMMU in the first place. Robin. > Signed-off-by: Magnus Damm > --- > > arch/arm64/mm/dma-mapping.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > --- 0001/arch/arm64/mm/dma-mapping.c > +++ work/arch/arm64/mm/dma-mapping.c 2017-01-23 20:54:40.060607110 +0900 > @@ -827,11 +827,19 @@ static bool do_iommu_attach(struct devic > struct iommu_domain *domain = iommu_get_domain_for_dev(dev); > > /* > + * In case IOMMU support is excluded from the kernel or if the device > + * is not hooked up to any IOMMU group then be silent and keep the > + * old dma_ops. > + */ > + if (!domain) > + return false; > + > + /* > * If the IOMMU driver has the DMA domain support that we require, > * then the IOMMU core will have already configured a group for this > * device, and allocated the default domain for that group. > */ > - if (!domain || iommu_dma_init_domain(domain, dma_base, size, dev)) { > + if (iommu_dma_init_domain(domain, dma_base, size, dev)) { > pr_warn("Failed to set up IOMMU for device %s; retaining platform DMA ops\n", > dev_name(dev)); > return false; > _______________________________________________ > iommu mailing list > iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu >