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[v6,00/11] KVM: xen: update shared_info and vcpu_info handling

Message ID 20230926122013.867391-1-paul@xen.org (mailing list archive)
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Series KVM: xen: update shared_info and vcpu_info handling | expand

Message

Paul Durrant Sept. 26, 2023, 12:20 p.m. UTC 
From: Paul Durrant <pdurrant@amazon.com>

The following text from the original cover letter still serves as an
introduction to the series:

"Currently we treat the shared_info page 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 we pointlessly invalidate and re-cache a
mapping to the *same page* of memory every time the guest requests that
shared_info be mapped into its address space. Let's avoid doing that by
modifying the pfncache code to allow activation using a fixed userspace HVA
as well as a GPA."

As with the previous version of the series, both the shared_info and
vcpu_info caches can now be activated using an HVA but the commit comment
on "map shared_info using HVA rather than GFN" has been extended to
explain why mapping shared_info using HVA is a particularly good idea.

This version of the series also includes an extra patch to "allow
vcpu_info content to be 'safely' copied. Currently there is a race window
when the VMM performs the copy; this patch allows the VMM to avoid that
race.

Paul Durrant (11):
  KVM: pfncache: add a map helper function
  KVM: pfncache: add a mark-dirty helper
  KVM: pfncache: add a helper to get the gpa
  KVM: pfncache: base offset check on khva rather than gpa
  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: allow vcpu_info content to be 'safely' copied

 Documentation/virt/kvm/api.rst                |  53 +++++--
 arch/x86/kvm/x86.c                            |   5 +-
 arch/x86/kvm/xen.c                            |  92 +++++++++----
 include/linux/kvm_host.h                      |  43 ++++++
 include/linux/kvm_types.h                     |   3 +-
 include/uapi/linux/kvm.h                      |   9 +-
 .../selftests/kvm/x86_64/xen_shinfo_test.c    |  59 ++++++--
 virt/kvm/pfncache.c                           | 129 +++++++++++++-----
 8 files changed, 302 insertions(+), 91 deletions(-)