On 01/02/19 00:28, Alexandro Sanchez Bach wrote:
> (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.
The missing handling is in the hypervisor:
if (ret == -EACCES) {
/*
* For some reason, during boot-up, Chrome OS guests make
hundreds of
* attempts to write to GPAs close to 4GB, which are mapped into
BIOS
* (read-only) and thus result in EPT violations.
* TODO: Handle this case properly.
*/
hax_warning("%s: Unexpected EPT violation cause. Skipping
instruction"
" (len=%u)\n", __func__, vcpu->vmx.exit_instr_length);
advance_rip(vcpu);
return HAX_EXIT;
}
> Also, this seems to be handled here:
> https://github.com/qemu/qemu/blob/15bede554162dda822cd762c689edb6fa32b6e3b/target/i386/hax-mem.c#L205-L207
Right, though to be precise it should be changed to
if (memory_region_is_rom(section->mr) ||
memory_region_is_romd(section->mr)) { flags |= HAX_RAM_INFO_ROM;
}
for that to work.
Paolo
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