Hi, > So... after playing with this thing for some time, it's become clear > that "MMIO traps" are painfully slow on the aarch64 platform we've been > working on (using KVM).
So, as we don't have compatibility requirements, and we also can't play tricks like using x86 string instructions: How about a completely different, dma-style interface for fw_cfg access? One register for the (physical) target address. One register for the transfer size. One register for the fw_cfg entry. Possibly one register for the fw_cfg offset (not really needed, but avoids the need for side effects such as writing fw_cfg entry register clearing the offset). One register to kick the transfer. cheers, Gerd
