This is all greek to me. I take it there's something wrong with these accelerators that makes (read-only?) flash memory not work, even though the read-only mapping we now create for traditional BIOS works. Weird, but I'm of course willing to take your word for it.
Yes, as I wrote in the other message even read-only flash memory supports commands, and these accelerators do not support direct reads + MMIO writes on the same memory slot. At least I checked HAX code and it doesn't; I don't know about WHPX.
(CC'd Yu Ning @ Intel's HAXM team) Not sure, if I'm understanding the issue correctly, but isn't `HAX_VM_IOCTL_SET_RAM2` with the `HAX_RAM_INFO_ROM` flag precisely what you are looking for? More precisely, HAX_VM_IOCTL_SET_RAM2 maps an HVA range to a GPA range, the HAX_RAM_INFO_ROM flag should allow only guest memory reads to that range [1]. When the guest attempts to write, this should trigger a VM exit that will be handled by QEMU. Also, this seems to be handled here: https://github.com/qemu/qemu/blob/15bede554162dda822cd762c689edb6fa32b6e3b/t... Best, Alexandro [1] https://github.com/intel/haxm/blob/master/docs/api.md