Re: [RFC PATCH v2 6/7] accel/kvm: Let KVM_EXIT_MMIO return error

[Peter Maydell]

On Mon, 18 May 2020 at 16:53, Philippe Mathieu-Daudé <address@hidden> wrote:
>
> Give the hypervisor a possibility to catch any error
> occuring during KVM_EXIT_MMIO.
>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> RFC because maybe we simply want to ignore this error instead

The "right" answer is that the kernel should enhance the KVM_EXIT_MMIO
API to allow userspace to say "sorry, you got a bus error on that
memory access the guest just tried" (which the kernel then has to
turn into an appropriate guest exception, or ignore, depending on
what the architecture requires.) You don't want to set ret to
non-zero here, because that will cause us to VM_STOP, and I
suspect that x86 at least is relying on the implict RAZ/WI
behaviour it currently gets.

thanks
-- PMM