Re: [Qemu-devel] [PATCH 2/3] s390: Virtual channel subsystem support.

[Marcelo Tosatti <mtosatti@redhat.com>]

Hi Cornelia,

On Wed, Oct 31, 2012 at 05:24:47PM +0100, Cornelia Huck wrote:
> Provide a mechanism for qemu to provide fully virtual subchannels to
> the guest. In the KVM case, this relies on the kernel's css support
> for I/O and machine check interrupt handling. The !KVM case handles
> interrupts on its own.
> 
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/s390x/Makefile.objs     |    1 +
>  hw/s390x/css.c             | 1209 ++++++++++++++++++++++++++++++++++++++++++++
>  hw/s390x/css.h             |   90 ++++
>  target-s390x/Makefile.objs |    2 +-
>  target-s390x/cpu.h         |  232 +++++++++
>  target-s390x/helper.c      |  146 ++++++
>  target-s390x/ioinst.c      |  737 +++++++++++++++++++++++++++
>  target-s390x/ioinst.h      |  213 ++++++++
>  target-s390x/kvm.c         |  251 ++++++++-
>  target-s390x/misc_helper.c |    6 +-
>  10 files changed, 2872 insertions(+), 15 deletions(-)
>  create mode 100644 hw/s390x/css.c
>  create mode 100644 hw/s390x/css.h
>  create mode 100644 target-s390x/ioinst.c
>  create mode 100644 target-s390x/ioinst.h

> +void kvm_s390_enable_css_support(CPUS390XState *env)
> +{
> +    struct kvm_enable_cap cap = {};
> +    int r;
> +
> +    /* Activate host kernel channel subsystem support. */
> +    if (kvm_enabled()) {
> +        /* One CPU has to run */
> +        s390_add_running_cpu(env);

Care to explain this?

> +
> +        cap.cap = KVM_CAP_S390_CSS_SUPPORT;
> +        r = kvm_vcpu_ioctl(env, KVM_ENABLE_CAP, &cap);
> +        assert(r == 0);
> +    }
> +}