Re: [PATCH v3 8/8] s390: guest support for diagnose 0x318

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 18 Jun 2020 18:22:58 -0400
Collin Walling <walling@linux.ibm.com> wrote:

> DIAGNOSE 0x318 (diag318) is an s390 instruction that allows the storage
> of diagnostic information that is collected by the firmware in the case
> of hardware/firmware service events.
> 
> QEMU handles the instruction by storing the info in the CPU state. A
> subsequent register sync will communicate the data to the hypervisor.
> 
> QEMU handles the migration via a VM State Description.
> 
> This feature depends on the Extended-Length SCCB (els) feature. If
> els is not present, then a warning will be printed and the SCLP bit
> that allows the Linux kernel to execute the instruction will not be
> set.
> 
> Availability of this instruction is determined by byte 134 (aka fac134)
> bit 0 of the SCLP Read Info block. This coincidentally expands into the
> space used for CPU entries, which means VMs running with the diag318
> capability may not be able to read information regarding all CPUs
> unless the guest kernel supports an extended-length SCCB.

We cannot do anything about that, I guess.

> 
> This feature is not supported in protected virtualization mode.
> 
> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> ---
>  hw/s390x/sclp.c                     |  5 +++++
>  include/hw/s390x/sclp.h             |  3 +++
>  target/s390x/cpu.h                  |  3 ++-
>  target/s390x/cpu_features.h         |  1 +
>  target/s390x/cpu_features_def.inc.h |  3 +++
>  target/s390x/cpu_models.c           |  1 +
>  target/s390x/gen-features.c         |  1 +
>  target/s390x/kvm.c                  | 31 +++++++++++++++++++++++++++++
>  target/s390x/machine.c              | 17 ++++++++++++++++
>  9 files changed, 64 insertions(+), 1 deletion(-)

LGTM.