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d="scan'208";a="480068519" Received: from sderix-mobl1.ger.corp.intel.com (HELO [10.214.213.131]) ([10.214.213.131]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Sep 2020 08:28:38 -0700 Subject: Re: [Intel-gfx] [PATCH 0/8] Convert the intel iommu driver to the dma-iommu api To: Logan Gunthorpe , Tom Murphy References: <20191221150402.13868-1-murphyt7@tcd.ie> <465815ae-9292-f37a-59b9-03949cb68460@deltatee.com> <20200529124523.GA11817@infradead.org> <33137cfb-603c-86e8-1091-f36117ecfaf3@deltatee.com> <766525c3-4da9-6db7-cd90-fb4b82cd8083@deltatee.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <60a82319-cbee-4cd1-0d5e-3c407cc51330@linux.intel.com> Date: Tue, 8 Sep 2020 16:28:35 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <766525c3-4da9-6db7-cd90-fb4b82cd8083@deltatee.com> Content-Language: en-US Cc: kvm@vger.kernel.org, David Airlie , dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, Julien Grall , Will Deacon , Jean-Philippe Brucker , linux-samsung-soc@vger.kernel.org, Marc Zyngier , Krzysztof Kozlowski , Jonathan Hunter , Christoph Hellwig , linux-rockchip@lists.infradead.org, Andy Gross , Gerald Schaefer , linux-s390@vger.kernel.org, linux-arm-msm@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-mediatek@lists.infradead.org, Matthias Brugger , Thomas Gleixner , virtualization@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, Robin Murphy , Cornelia Huck , Linux Kernel Mailing List , iommu@lists.linux-foundation.org, Kukjin Kim , David Woodhouse X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi, On 27/08/2020 22:36, Logan Gunthorpe wrote: > On 2020-08-23 6:04 p.m., Tom Murphy wrote: >> I have added a check for the sg_dma_len == 0 : >> """ >> } __sgt_iter(struct scatterlist *sgl, bool dma) { >> struct sgt_iter s = { .sgp = sgl }; >> >> + if (sgl && sg_dma_len(sgl) == 0) >> + s.sgp = NULL; >> >> if (s.sgp) { >> ..... >> """ >> at location [1]. >> but it doens't fix the problem. > > Based on my read of the code, it looks like we also need to change usage > of sgl->length... Something like the rough patch below, maybe? This thread was brought to my attention and I initially missed this reply. Essentially I came to the same conclusion about the need to use sg_dma_len. One small correction below: > Also, Tom, do you have an updated version of the patchset to convert the > Intel IOMMU to dma-iommu available? The last one I've found doesn't > apply cleanly (I'm assuming parts of it have been merged in slightly > modified forms). > > Thanks, > > Logan > > -- > > diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h > b/drivers/gpu/drm/i915/i915 > index b7b59328cb76..9367ac801f0c 100644 > --- a/drivers/gpu/drm/i915/i915_scatterlist.h > +++ b/drivers/gpu/drm/i915/i915_scatterlist.h > @@ -27,13 +27,19 @@ static __always_inline struct sgt_iter { > } __sgt_iter(struct scatterlist *sgl, bool dma) { > struct sgt_iter s = { .sgp = sgl }; > > + if (sgl && !sg_dma_len(s.sgp)) I'd extend the condition to be, just to be safe: if (dma && sgl && !sg_dma_len(s.sgp)) > + s.sgp = NULL; > + > if (s.sgp) { > s.max = s.curr = s.sgp->offset; > - s.max += s.sgp->length; > - if (dma) > + > + if (dma) { > + s.max += sg_dma_len(s.sgp); > s.dma = sg_dma_address(s.sgp); > - else > + } else { > + s.max += s.sgp->length; > s.pfn = page_to_pfn(sg_page(s.sgp)); > + } Otherwise has this been tested or alternatively how to test it? (How to repro the issue.) Regards, Tvrtko _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu