On 5/31/2019 8:43 AM, Herbert Xu wrote: > On Fri, May 31, 2019 at 05:22:50AM +0000, Horia Geanta wrote: >> >> Unless it's clearly defined *which* virtual addresses mustn't be accessed, >> things won't work properly. >> In theory, any two objects could share a cache line. We can't just stop all >> memory accesses from CPU while a peripheral is busy. > > The user obviously can't touch the memory areas potentially under > DMA. But in this case it's not the user that's doing it, it's > the driver. > > So the driver must not touch any virtual pointers given to it > as input/output while the DMA areas are mapped. > Driver is not touching the DMA mapped areas, the DMA API conventions are carefully followed. It's touching a virtual pointer that is not DMA mapped, that just happens to be on the same cache line with a DMA mapped buffer. Thanks, Horia
