kvm-s390: revised version of kvm-s390 guest memory handling - v4

From: Christian Ehrhardt <[email protected]>

*updates in v3*
- ensure kick allocations (might_sleep) are out of atomic context
- replaced "kick to level" behaviour by "kick to low level and bail out"
- updates on running vcpus can now be handled without need to rerun the vcpu
- kvm_arch_set_memory_region waits until the update is consumed by the vcpu
- kickout only scheduled vcpus (wait might hang forever on non-scheduled vcpus)
- moved some code between patches 1 & 2 thematically
- update vcpu->cpu in kvm-s390 arch handler for load/put
- remove a redundant declaration in kvm_host.h related to load/put

Note: further unification of make_all_cpu_request and the kick mechanism is planned, but it might be good to split it from this step towards commonality.

*updates in v2*
added optimization to patch 3/3 to skip (addtional) kickout of vcpu's that had the request already set.

This patch series results from our discussions about handling memslots and vcpu mmu reloads. It streamlines kvm-s390 a bit by using slots_lock, vcpu-request (KVM_REQ_MMU_RELOAD) and a kick mechanism to ensure vcpus come out of guest context to catch the update.

I tested the reworked code a while with multiple smp guests and some extra code that periodically injects kicks and/or mmu reload requests, but I'm happy about every additional review feedback.

Patches included:
Subject: [PATCH 1/5] kvm-s390: infrastructure to kick vcpus out of guest state - v3
Subject: [PATCH 2/5] kvm-s390: fix interruption casued by signal - v2
Subject: [PATCH 3/5] kvm-s390: update vcpu->cpu
Subject: [PATCH 4/5] kvm: remove redundant declarations
Subject: [PATCH 5/5] kvm-s390: streamline memslot handling - v4

Overall-Diffstat:

 arch/s390/include/asm/kvm_host.h |    9 ++---
 arch/s390/kvm/gaccess.h          |   23 ++++++------
 arch/s390/kvm/intercept.c        |   20 +++++++----
 arch/s390/kvm/kvm-s390.c         |   70 ++++++++++++++++++++-------------------
 arch/s390/kvm/kvm-s390.h         |   50 +++++++++++++++++++++++++++
 arch/s390/kvm/sigp.c             |   63 ++++++++++++++++++++++++-----------
 include/linux/kvm_host.h         |    2 -
 7 files changed, 159 insertions(+), 78 deletions(-)