Re: [Qemu-devel] [PATCH v1 5/7] s390x/tcg: implement SET CLOCK

[Cornelia Huck <cohuck@redhat.com>]

On Fri, 25 May 2018 13:37:06 +0200
David Hildenbrand <david@redhat.com> wrote:

> This allows a guest to change its TOD. We already take care of updating
> all CKC timers from within S390TODClass.
> 
> Use MO_ALIGN to load the operand manually - this will properly trigger a
> SPECIFICATION exception.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/helper.h      |  1 +
>  target/s390x/insn-data.def |  3 +--
>  target/s390x/misc_helper.c | 19 +++++++++++++++++++
>  target/s390x/translate.c   |  9 +++++++++
>  4 files changed, 30 insertions(+), 2 deletions(-)
> 

> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
> index 2ef9de1cca..2f5cd6d22a 100644
> --- a/target/s390x/misc_helper.c
> +++ b/target/s390x/misc_helper.c
> @@ -191,6 +191,25 @@ void tcg_s390_tod_updated(CPUState *cs, run_on_cpu_data opaque)
>      helper_sckc(env, env->ckc);
>  }
>  
> +/* Set Clock */
> +uint32_t HELPER(sck)(CPUS390XState *env, uint64_t tod_low)
> +{
> +    S390TODState *td = s390_get_tod();
> +    S390TODClass *tdc = S390_TOD_GET_CLASS(td);

Would it make sense to cache the class as well?

> +    S390TOD tod = {
> +        .high = 0,
> +        .low = tod_low,
> +    };
> +    Error *err = NULL;
> +
> +    qemu_mutex_lock_iothread();
> +    tdc->set(td, &tod, &err);
> +    qemu_mutex_unlock_iothread();
> +    g_assert(!err);
> +
> +    return 0;
> +}
> +