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Tsirkin" Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops Message-ID: <20200429033539.GB5097@quicinc.com> References: <1588073958-1793-1-git-send-email-vatsa@codeaurora.org> <1588073958-1793-6-git-send-email-vatsa@codeaurora.org> <20200428121232-mutt-send-email-mst@kernel.org> <20200428174952.GA5097@quicinc.com> <20200428163448-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200428163448-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) Cc: tsoni@codeaurora.org, virtio-dev@lists.oasis-open.org, konrad.wilk@oracle.com, jan.kiszka@siemens.com, jasowang@redhat.com, christoffer.dall@arm.com, virtualization@lists.linux-foundation.org, alex.bennee@linaro.org, iommu@lists.linux-foundation.org, stefano.stabellini@xilinx.com, will@kernel.org, linux-kernel@vger.kernel.org, pratikp@codeaurora.org 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: , Reply-To: Srivatsa Vaddagiri Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" * Michael S. Tsirkin [2020-04-28 16:41:04]: > > Won't we still need some changes to virtio to make use of its own pool (to > > bounce buffers)? Something similar to its own DMA ops proposed in this patch? > > If you are doing this for all devices, you need to either find a way > to do this without chaning DMA ops, or by doing some automatic change > to all drivers. Ok thanks for this input. I will see how we can obfuscate this in DMA APIs itself. Can you also comment on the virtio transport problem I cited? The hypervisor we are dealing with does not support MMIO transport. It supports message queue send/recv and also doorbell, which I think can be used if we can make some change like this to virtio_mmio.c: +static inline u32 +virtio_readl(struct virtio_mmio_device *vm_dev, u32 reg_offset) +{ + return vm_dev->mmio_ops->readl(vm_dev, reg_offset); +} + +static inline void +virtio_writel(struct virtio_mmio_device *vm_dev, u32 reg_offset, u32 data) +{ + vm_dev->mmio_ops->writel(vm_dev, reg_offset, data); +} /* Check magic value */ - magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE); + magic = vrito_readl(vm_dev, VIRTIO_MMIO_MAGIC_VALUE); mmio_ops->readl on most platforms can default to readl itself, while on a platform like us, it can boil down to message_queue send/recv. Would such a change be acceptable? -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu