Re: [PATCH v7 00/15] KVM: s390: make use of the GIB

Christian Borntraeger
2019-02-06T17:09:51Z

Series Applied and queued.
see https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux.git/log/?h=next

On 31.01.2019 09:52, 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.
>
> 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(-)
>