Hi, Last year while I was implementing a virtio-rpmb backend for QEMU I ended up using patches from the ACRN tree which was based on Thomas' patches last posted in 2016: https://lore.kernel.org/lkml/1478548394-8184-1-git-send-email-tomas.winkler@xxxxxxxxx/ which I bastardised into a testing tree on a more recent kernel: https://git.linaro.org/people/alex.bennee/linux.git/log/?h=testing/virtio-rpmb The main reason I hacked them around was because the VirtIO spec had since been finalised and had a very different framing structure. The original proposed ABI provided for an ioctl which sent JDEC frames to the underlying device. This was later expanded to support NVME style frames. Neither of these frame sequences matched the final VirtIO specification. It seems to me having the ioctl ABI at this level exposes too many underlying HW details to user space. With the number of HW devices that providing RPMB features likely to grow from the current 3 (eMMC/JDEC, NVME, VirtIO) it seems this ABI should operate at a higher level, e.g.: PROGRAM_KEY GET_WRITE_COUNTER WRITE_DATA READ_DATA and I guess some sort of asynchronous result check? It would then be for the kernel to take the higher level concepts and translate them to the final frames required to talk to the actual HW (if indeed there is some). Does this seem reasonable? Is this orthogonal to any access to RPMB partitions that file-systems might want to do? -- Alex Bennée
