Re: [PATCH v4 00/10] KVM: s390: make use of the GIB

[Christian Borntraeger <borntraeger@de.ibm.com>]

FWIW, Assuming that Michael addresses the small comments of Cornelia I will
apply the next version to kvms390/next. As we touch common s390/cio/ code 
this will be a topic branch that I will merge. In case of conflicts Martin 
can then also merge this. If there are no conflicts then this will only
go via the kvms390 tree.



On 30.11.2018 15:32, Michael Mueller wrote:
> The Guest Information Area (GIB) and its mechanics is part of
> the AIV facility. It provides hardware support to process
> Adapter Interruptions (AI) for pagable storage mode guests. 
> 
> Whenever a guest cannot process an AI because none of its
> vcpus is running in SIE context, a GIB alert interruption is
> sent to and handled by the host program to dispatch a vcpu of
> the respective guest.
> 
> Eventually, the AI is handled by the guest.
> 
> v3->v4:
>   The central change of v4 is that the metric "vcpus_in_sie"
>   has been dropped. A least agressive IAM restore strategy
>   is being followed now. The consequence is that potentially
>   more GAL interruptions are to be handled by the host program.
>   The assuption as made that as soon the first vcpu is trying
>   to go into wait state, this could be the last vcpu being
>   open for I/O interruptions. Thus, to not loose the initiative
>   to deliver I/O interruptions as soon as possible, the IAM
>   is restored. Adding better heuristics can be done in future.
> 
>   I expect this to be the last version of the series.
>  
>   patch 01/12: Kernel msg now printed when FLIC fails
>                to register during arch inititialization.
>   patch 03/12: Commit message slightly changed with the
>   	       hint that gib initialization is called
> 	       by last patch of this serias.
>   patch 09/12: IAM now restored during kvm_s390_handle_wait()
>   patch 10/12: gib destroy case now handled upon unsuccessful
>   	       arch inititialization.
> 
> All other patches are unchanged.
> 
> v2->v3:
>   patch 01/12: Fixes a resource dealocation issue upon
>   	       unsuccessful exit from kvm_arch_init().
> 	       It is relevant for patch 11/12 as well. 
>   patch 08/12: The function process_gib_alert_list() has
>                been rewritten to reduce the number of GAL
> 	       interruptions on the host for many guest
> 	       scenarios.
>   patch 10/12: The IAM is now never cleared before SIE entry.
>                It will be cleared by millicode as soon the
> 	       first guest interruption is made pending and
> 	       not directly processed in SIE. The IAM gets
> 	       restored as soon a vm is idle, i.e. no vcpu
> 	       of that guest is in SIE context anymore.
>   patch 11/12: now integrates with new patch 01/12
>   patch 12/12: This patch is just experimental and shall not
>                be part of the final series.
> 
> The first patch of series v2: "leave AIs in IPM of GISA
> during vcpu_pre_run()" has been dropped.
> 
> All other patches are unchanged.
> 
> v1->v2:
>   patch 01/12: New patch. Tt can go also standalone without the
>   	       rest of the GIB series presented here but is a
> 	       requirement 
>   patch 03/12: kvm_s390_gib_init() now has a return code
>   patch 06/12: unlink_gib_alert_list() now uses cmpxchg() instead
>     	       of atomic_xchg()
>   patch 08/12: New patch. Foctors out __find_vcpu_for_floating_irq()
>   patch 09/12: process_gib_alert_list() has been simplified
>                the GISA clear/destroy cases have been removed
>   patch 11/12: kvm_s390_gisa_clear/destroy() now clear the IAM
>                and process the alert list directly
> 	       The IAM now gets restored in vcpu_post_run() only if
> 	       the GISA is not in alert list
>   patch 12/12: during kvm_arch_init() now the return code of
>     	       kvm_s390_gib_init() is honored.
> 
> All other patches are unchanged.
> 
> Michael Mueller (10):
>   KVM: s390: unregister debug feature on failing arch init
>   s390/cio: add function chsc_sgib()
>   KVM: s390: add the GIB and its related life-cyle functions
>   KVM: s390: factor out nullify_gisa()
>   KVM: s390: add kvm reference to struct sie_page2
>   KVM: s390: factor out __find_vcpu_for_floating_irq()
>   KVM: s390: add function process_gib_alert_list()
>   KVM: s390: add functions to (un)register GISC with GISA
>   KVM: s390: add and wire function gib_alert_irq_handler()
>   KVM: s390: start using the GIB
> 
>  Documentation/kmsg/s390/kvm      |  24 +++++
>  arch/s390/include/asm/cio.h      |   1 +
>  arch/s390/include/asm/irq.h      |   1 +
>  arch/s390/include/asm/isc.h      |   1 +
>  arch/s390/include/asm/kvm_host.h |  19 +++-
>  arch/s390/kernel/irq.c           |   1 +
>  arch/s390/kvm/interrupt.c        | 214 +++++++++++++++++++++++++++++++++++++--
>  arch/s390/kvm/kvm-s390.c         |  27 ++++-
>  arch/s390/kvm/kvm-s390.h         |   7 ++
>  drivers/s390/cio/chsc.c          |  37 +++++++
>  drivers/s390/cio/chsc.h          |   1 +
>  11 files changed, 318 insertions(+), 15 deletions(-)
>  create mode 100644 Documentation/kmsg/s390/kvm
>