[v8,00/15] KVM: xen: update shared_info and vcpu_info handling

Message

Paul Durrant Nov. 21, 2023, 6:02 p.m. UTC

From: Paul Durrant <[e-mail]>

Currently the shared_info page is treated as guest memory and the VMM
informs KVM of its location using a GFN. However it is not guest memory as
such; it's an overlay page. So the pfncache is pointlessly invalidated and
re-activated to create a new mapping of the *same page* of memory every
time the guest requests that shared_info be mapped into its address space.
Avoid doing that by modifying the pfncache code to allow activation using
a fixed userspace HVA as well as a GPA.

Version 8 of the series has been substantially re-worked and includes
several clean-up patches, particlarly the non-trivial clean-up patches:
"pfncache: remove KVM_GUEST_USES_PFN usage" and "xen: split up
kvm_xen_set_evtchn_fast()". Each patch carries its own version history.

Paul Durrant (15):
  KVM: pfncache: Add a map helper function
  KVM: pfncache: remove unnecessary exports
  KVM: xen: mark guest pages dirty with the pfncache lock held
  KVM: pfncache: add a mark-dirty helper
  KVM: pfncache: remove KVM_GUEST_USES_PFN usage
  KVM: pfncache: stop open-coding offset_in_page()
  KVM: pfncache: include page offset in uhva and use it consistently
  KVM: pfncache: allow a cache to be activated with a fixed (userspace)
    HVA
  KVM: xen: allow shared_info to be mapped by fixed HVA
  KVM: xen: allow vcpu_info to be mapped by fixed HVA
  KVM: selftests / xen: map shared_info using HVA rather than GFN
  KVM: selftests / xen: re-map vcpu_info using HVA rather than GPA
  KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability
  KVM: xen: split up kvm_xen_set_evtchn_fast()
  KVM: xen: allow vcpu_info content to be 'safely' copied

 Documentation/virt/kvm/api.rst                |  53 +++-
 arch/x86/kvm/x86.c                            |   7 +-
 arch/x86/kvm/xen.c                            | 260 +++++++++++-------
 include/linux/kvm_host.h                      |  38 ++-
 include/linux/kvm_types.h                     |   8 -
 include/uapi/linux/kvm.h                      |   9 +-
 .../selftests/kvm/x86_64/xen_shinfo_test.c    |  59 +++-
 virt/kvm/pfncache.c                           | 175 ++++++------
 8 files changed, 374 insertions(+), 235 deletions(-)


base-commit: 45b890f7689eb0aba454fc5831d2d79763781677
---
Cc: Borislav Petkov <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: David Woodhouse <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: Sean Christopherson <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]