Re: [PATCH] s390x: do a subsystem reset before the unprotect on reboot

[Viktor Mihajlovski]

On Fri, 2023-09-01 at 11:48 +0000, Janosch Frank wrote:
> Bound APQNs have to be reset before tearing down the secure config via
> s390_machine_unprotect(). Otherwise the Ultravisor will return a error
> code.
> 
> So let's do a subsystem_reset() which includes a AP reset before the
> unprotect call. We'll do a full device_reset() afterwards which will
> reset some devices twice. That's ok since we can't move the
> device_reset() before the unprotect as it includes a CPU clear reset
> which the Ultravisor does not expect at that point in time.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
> 
> I'm not able to test this for the PV AP case right new, that has to
> wait to early next week. However Marc told me that the non-AP PV test
> works fine now.
> 
> ---
>  hw/s390x/s390-virtio-ccw.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 3dd0b2372d..2d75f2131f 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -438,10 +438,20 @@ static void s390_machine_reset(MachineState *machine, 
> ShutdownCause reason)
>      switch (reset_type) {
>      case S390_RESET_EXTERNAL:
>      case S390_RESET_REIPL:
> +        /*
> +         * Reset the subsystem which includes a AP reset. If a PV
> +         * guest had APQNs attached the AP reset is a prerequisite to
> +         * unprotecting since the UV checks if all APQNs are reset.
> +         */
> +        subsystem_reset();
>          if (s390_is_pv()) {
>              s390_machine_unprotect(ms);
>          }
>  
> +        /*
> +         * Device reset includes CPU clear resets so this has to be
> +         * done AFTER the unprotect call above.
> +         */
>          qemu_devices_reset(reason);
>          s390_crypto_reset();
>  
I tested this with and without bound/associated APQNs both with booting
from disk and with direct kernel boot. Subsequent reboots are correctly
resetting the APQNs. I also successfully tested the case direct kernel
boot -> chreipl -> disk boot.

If you want you can add
  Tested-by: Viktor Mihajlovski <mihajlov@linux.ibm.com>