On Tue, Mar 17, 2020 at 09:53:17AM -0300, Jason Gunthorpe wrote: > > Thinking out loud a bit more: > > > > - do we really need HMM_PFN_ERROR, or is just a return value from > > hmm_range_fault enough? > > I'm not totally clear on this. The only use for ERROR is to signal to a > non-faulting hmm_range_fault (ie shapshot) that the page should generate a > device fault (ie device SIGSEGV). > > We can also handle ERROR by having the device take the fault to CPU, > then fail during a faulting hmm_range_fault and then dropping the > ERROR indication toward the device. > > If we already know the page cannot be faulted when we read it it feels > natural to return that too. True. Of course we could just stick an ERR_PTR into the page array in this case. > > - because if it is we don't need output flags at all, and the output > > array could be struct pages, which would make for a much easier > > to use API > > valid and write is required for the non-faulting case, I don't > think flags can go away. Do we have any cases where these aren't simply kept from the input array? I couldn't find any, but I've not understood some of the subtle details before.
