On Sun, Sep 27, 2020 at 07:58:29AM +0000, Sherry Sun wrote: > Thanks for your reply. > Can you explain why we cannot use the API and header above in drivers? > And do you know if there are any APIs that could replace this to check the > device hardware dma coherent support?
If your treat the memory as if it is coherent with device access you should always use dma_alloc_coherent. The whole point of the DMA API is to abstract such differences away. > > > > > + vdev->vvr[i].vrh.vring.used = > > > + (void __force *)vpdev->hw_ops->remap( > > > > And you must not use __force casts without a comment explanation why > > they are safe. > > Here is the original code, I moved the original code into the if() without > change it. > But I think this is because vpdev->hw_ops->remap() return type is void > __iomem *, but vring.used need type void *. > Maybe this is a workaround for Intel MIC platform, as it reassigns the used > ring on the EP side. Well, we'll need to figure out what is going on here, and blind casts to and from __iomem are dangerous.
