[PATCH 0/9] arm64: KVM: debug infrastructure support

[Peter Maydell]

On 19 May 2014 10:28, Marc Zyngier <marc.zyngier at arm.com> wrote:
> If you look carefully at patch #8 (last hunk of the patch), you'll see
> that I always reset the debug state to "clean" at the end of a guest
> run:
>
> @@ -609,6 +1040,12 @@ __kvm_vcpu_return:
>
>         bl __restore_sysregs
>         bl __restore_fpsimd
> +
> +       skip_clean_debug_state x3, 1f
> +       // Clear the dirty flag for the next run
> +       str     xzr, [x0, #VCPU_DEBUG_FLAGS]
> +       bl      __restore_debug
> +1:
>         restore_host_regs
>
>         mov     x0, x1
>
> This ensures that the guest's debug state will only be reloaded if:
>
> - MDSCR_EL1 has either MDE or KDE set (which means the guest is actively
> using the debug infrastructure)
> - or the guest has written to a trapped register (which marks the state
> as dirty).

Do we also handle the case where the guest didn't
write to the trapped register but userspace did (via
the SET_ONE_REG API)? Maybe this just falls out in the
wash or is handled already...

thanks
-- PMM