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From:   Michael Mueller <mimu@linux.ibm.com>
To:     KVM Mailing List <kvm@vger.kernel.org>
Cc:     Linux-S390 Mailing List <linux-s390@vger.kernel.org>,
        linux-kernel@vger.kernel.org,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Halil Pasic <pasic@linux.ibm.com>,
        Pierre Morel <pmorel@linux.ibm.com>,
        Michael Mueller <mimu@linux.ibm.com>
Subject: [PATCH v7 00/15] KVM: s390: make use of the GIB
Date:   Thu, 31 Jan 2019 09:52:31 +0100
Message-Id: <20190131085247.13826-1-mimu@linux.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

v6->v7:
  patches 1/15 to 7/15
     prepare the existing Interruption and GISA code for
     the introduction of the GIB code. (kept from v6)
  patches 8/15 to 10/15
     kept from v6.
  patch 11/15
     kvm_s390_gisc_register() now uses a single conditional
     branch to extend IAM restore value and to set the IAM
     in GISA. 
  patch 12/15
     kvm_s390_clear_gisa() now refactored in its own patch.
  patch 13/15
     I'm keeping the 50 usec timer expiration as the statistic
     data shows a single timer restart only.
       gisa_get_ipm_or_restore_iam() now called when entering
     kvm_s390_handle_wait(). That saves some of the timer
     restarts.
       Some modifications in kvm_s390_gisa_destroy()
  patch 14/15
     kept from v6.
  patch 15/15
     additional test on non NULL gisa origin in pending_irqs()

v5->v6:
  Futher significant change was introduced with this version
  now:

  a) During the alert list processing now a hrtimer is
     started to kick an idle vcpu with open I/O interrupt
     mask. It then is restarted to monitor the interruption
     consumption and when the IPM is clean (no relevant
     ISCs pending anymore) atomically restores the IAM
     and don't restarts or if new ISCs arrive kick other
     idle vcpus.

  patches 1/13 to 7/13:
     prepare the existing Interruption and GISA code for
     the introduction of the GIB code.
  patches 8/13 to 10/13:
     kept from v5.
  patch 11/13:
     Some comments added.
  patch 12/13:
     Significatly changed due to the hrtimer control.
  patch 13/13:
     Basically kept from v5 except for a slight reordering
     that shortens the patch.

v4->v5:
  Between these two versions some significant change was
  introduced:

  a) During IPM look-up, the IAM gets atomically restored
     if the IPM is clean. (The main strategy is: As soon no
     airqs are pending anymore, get prepared for new ones
     arriving).

  b) Kick a set of vcpus in WAIT state, that will be able
     to handle all ISCs in IPM if possible. The main loop
     that processes the GIB alert list is unchanged.

  patches 1/15 to 6/15:
     prepare the existing Interruption and GISA code for
     the introduction of the GIB code.
  patches 7/15 to 9/15:
     kept from v4. 
  patch 10/15:
     restores the IAM in get_ipm() when clean on request
     with additional parameter irq_flags
  patch 12/15:
     modifies kvm_s390_deliver_pending_interrupts() such
     that the IAM is not restored during the deliverable_irqs()
     test as we are about to enter the SIE. Restoring the
     IAM would trigger the alert mechanism unnecessarily
     on SIE entry.
  patch 13/15:
     process_gib_alert_list() now triggers a minimal set
     of idle vcpus capable the handle all pending ISCs.
  patch 14/15:
     the wiring is logical similar to v4 but uses different
     routines
  patch 15/15: 
     kept from v4. 

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 (15):
  KVM: s390: drop obsolete else path
  KVM: s390: make bitmap declaration consistent
  KVM: s390: move bitmap idle_mask into arch struct top level
  KVM: s390: coding style kvm_s390_gisa_init/clear()
  KVM: s390: use pending_irqs_no_gisa() where appropriate
  KVM: s390: remove kvm_s390_ from gisa static inline functions
  KVM: s390: introduce struct kvm_s390_gisa_interrupt
  s390/cio: add function chsc_sgib()
  KVM: s390: add the GIB and its related life-cyle functions
  KVM: s390: add kvm reference to struct sie_page2
  KVM: s390: add functions to (un)register GISC with GISA
  KVM: s390: kvm_s390_gisa_clear() now clears the IPM only
  KVM: s390: add gib_alert_irq_handler()
  KVM: s390: start using the GIB
  KVM: s390: fix possible null pointer dereference in pending_irqs()

 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 |  36 +++-
 arch/s390/kernel/irq.c           |   1 +
 arch/s390/kvm/interrupt.c        | 431 +++++++++++++++++++++++++++++++++++----
 arch/s390/kvm/kvm-s390.c         |  13 +-
 arch/s390/kvm/kvm-s390.h         |   4 +-
 drivers/s390/cio/chsc.c          |  37 ++++
 drivers/s390/cio/chsc.h          |   1 +
 10 files changed, 480 insertions(+), 46 deletions(-)

-- 
2.13.4