[v1,00/16] KVM: Add Xen event channel acceleration

Message

David Woodhouse Feb. 24, 2022, 12:48 p.m. UTC

This series adds event channel acceleration for Xen guests. In particular
it allows guest vCPUs to send each other IPIs without having to bounce
all the way out to the userspace VMM in order to do so. Likewise, the
Xen singleshot timer is added, and a version of SCHEDOP_poll. Those
major features are based on Joao and Boris' patches from 2019.

Cleaning up the event delivery into the vcpu_info involved using the new
gfn_to_pfn_cache for that, and that means I ended up doing so for *all*
the places the guest can have a pvclock. There's a slight wart there,
in that we now need to explicitly *clear* the dirty flag in the cache
in kvm_xen_destroy_vcpu() to prevent the page being marked dirty from
that context when there's no active vCPU — otherwise it would trigger
the warning I added in commit 2efd61a608. That's actually OK for the
Xen case since the VMM will always know where the regions are and it's
reasonable to declare that they should be considered 'always dirty'.

I want to give that deferred dirty marking a little more thought for
the general case of the gfn_to_pfn_cache though.

Changes since my 'v0' proof-of-concept series to invite early heckling:
 • Drop the runstate fix which is merged now.
 • Add Sean's gfn_to_pfn_cache API change at the start of the series.
 • Add KVM self tests
 • Minor bug fixes

Boris Ostrovsky (1):
      KVM: x86/xen: handle PV spinlocks slowpath

David Woodhouse (11):
      KVM: x86/xen: Use gfn_to_pfn_cache for runstate area
      KVM: x86: Use gfn_to_pfn_cache for pv_time
      KVM: x86/xen: Use gfn_to_pfn_cache for vcpu_info
      KVM: x86/xen: Use gfn_to_pfn_cache for vcpu_time_info
      KVM: x86/xen: Make kvm_xen_set_evtchn() reusable from other places
      KVM: x86/xen: Support direct injection of event channel events
      KVM: x86/xen: Add KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID
      KVM: x86/xen: Kernel acceleration for XENVER_version
      KVM: x86/xen: Support per-vCPU event channel upcall via local APIC
      KVM: x86/xen: Advertise and document KVM_XEN_HVM_CONFIG_EVTCHN_SEND
      KVM: x86/xen: Add self tests for KVM_XEN_HVM_CONFIG_EVTCHN_SEND

Joao Martins (3):
      KVM: x86/xen: intercept EVTCHNOP_send from guests
      KVM: x86/xen: handle PV IPI vcpu yield
      KVM: x86/xen: handle PV timers oneshot mode

Sean Christopherson (1):
      KVM: Use enum to track if cached PFN will be used in guest and/or host

 Documentation/virt/kvm/api.rst                     |  129 +-
 arch/x86/include/asm/kvm_host.h                    |   23 +-
 arch/x86/kvm/irq.c                                 |   11 +-
 arch/x86/kvm/irq_comm.c                            |    2 +-
 arch/x86/kvm/x86.c                                 |  123 +-
 arch/x86/kvm/xen.c                                 | 1257 ++++++++++++++++----
 arch/x86/kvm/xen.h                                 |   69 +-
 include/linux/kvm_host.h                           |   14 +-
 include/linux/kvm_types.h                          |   10 +-
 include/uapi/linux/kvm.h                           |   43 +
 .../testing/selftests/kvm/x86_64/xen_shinfo_test.c |  340 +++++-
 virt/kvm/pfncache.c                                |   14 +-
 12 files changed, 1700 insertions(+), 335 deletions(-)