On 07/27/2018 03:28 PM, Will Deacon wrote: > Hi Anshuman, > > On Fri, Jul 20, 2018 at 09:29:37AM +0530, Anshuman Khandual wrote: >> This patch series is the follow up on the discussions we had before about >> the RFC titled [RFC,V2] virtio: Add platform specific DMA API translation >> for virito devices (https://patchwork.kernel.org/patch/10417371/). There >> were suggestions about doing away with two different paths of transactions >> with the host/QEMU, first being the direct GPA and the other being the DMA >> API based translations. >> >> First patch attempts to create a direct GPA mapping based DMA operations >> structure called 'virtio_direct_dma_ops' with exact same implementation >> of the direct GPA path which virtio core currently has but just wrapped in >> a DMA API format. Virtio core must use 'virtio_direct_dma_ops' instead of >> the arch default in absence of VIRTIO_F_IOMMU_PLATFORM flag to preserve the >> existing semantics. The second patch does exactly that inside the function >> virtio_finalize_features(). The third patch removes the default direct GPA >> path from virtio core forcing it to use DMA API callbacks for all devices. >> Now with that change, every device must have a DMA operations structure >> associated with it. The fourth patch adds an additional hook which gives >> the platform an opportunity to do yet another override if required. This >> platform hook can be used on POWER Ultravisor based protected guests to >> load up SWIOTLB DMA callbacks to do the required (as discussed previously >> in the above mentioned thread how host is allowed to access only parts of >> the guest GPA range) bounce buffering into the shared memory for all I/O >> scatter gather buffers to be consumed on the host side. >> >> Please go through these patches and review whether this approach broadly >> makes sense. I will appreciate suggestions, inputs, comments regarding >> the patches or the approach in general. Thank you. > I just wanted to say that this patch series provides a means for us to > force the coherent DMA ops for legacy virtio devices on arm64, which in turn > means that we can enable the SMMU with legacy devices in our fastmodel > emulation platform (which is slowly being upgraded to virtio 1.0) without > hanging during boot. Patch below. > > So: > > Acked-by: Will Deacon <will.deacon@xxxxxxx> > Tested-by: Will Deacon <will.deacon@xxxxxxx> Thanks Will. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
