On Tue, Oct 20, 2020 at 10:01:41PM -0700, Furquan Shaikh wrote: > GSMI driver uses dma_pool_* API functions for buffer allocation > because it requires that the SMI buffers are allocated within 32-bit > physical address space. However, this does not work well with IOMMU > since there is no real device and hence no domain associated with the > device. > > Since this is not a real device, it does not require any device > address(IOVA) for the buffer allocations. The only requirement is to > ensure that the physical address allocated to the buffer is within > 32-bit physical address space. This change allocates a page using > `get_zeroed_page()` and passes in GFP_DMA32 flag to ensure that the > page allocation is done in the DMA32 zone. All the buffer allocation > requests for gsmi_buf are then satisfed using this pre-allocated page > for the device.
Are you sure that "GFP_DMA32" really does what you think it does? A "normal" call with GFP_KERNEL" will give you memory that is properly dma-able. We should not be adding new GFP_DMA* users in the kernel in these days, just call dma_alloc*() and you should be fine. thanks, greg k-h
