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Michael Kelley
ab96bc97cd
In current code, the coherent_dma_mask for VMBus devices is not set, so it has the default value of 0, which essentially means "invalid". Because drivers for VMBus devices do not use dma_alloc_*() functions, the usual use of the coherent mask does not occur, and no errors result. However, a valid coherent_dma_mask may be needed even though the drivers don't use dma_alloc_*() functions. In a CoCo VM, the VMBus storvsc and netvsc drivers must bounce buffer DMA operations through the swiotlb because the Hyper-V host can't DMA into encrypted guest memory. If the kernel is built with CONFIG_SWIOTLB_DYNAMIC and the initial swiotlb size is small, swiotlb code may need to grow the swiotlb in response to a DMA mapping request. That growth first allocates a transient pool while the swiotlb is expanded in the background. The transient pool memory is allocated from the DMA atomic pools, and the allocation code checks for a valid coherent_dma_mask. With current code, this check fails, then the DMA mapping request from the storvsc or netvsc driver fails, and finally an I/O error occurs. Fix this problem by setting coherent_dma_mask for VMBus devices at the same time that dma_mask is set. Being a synthetic bus, VMBus does not have any restrictions on coherent DMA, so the coherent mask is set to the full 64 bits for all VMBus devices, just like with dma_mask. Signed-off-by: Michael Kelley <mhklinux@outlook.com> Signed-off-by: Wei Liu <wei.liu@kernel.org>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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