[RFC,v2,00/10] RFCv2: nested AVIC

Message

Maxim Levitsky April 21, 2022, 5:12 a.m. UTC

This patch series implement everything that is needed to
use AMD's AVIC while a nested guest is running including
ability of the nested guest to use it, and brings feature
parity vs APICv.

Compared to v1 of the series, there are lot of fixes,
and refactoring.

This version still use unconditional read-only apic id,
which will be addressed in the next version.

For the last patch, which allows to avoid cleaning is_running
bit in physid pages as long as it is possible, I measured
what would happen in a worst case:

- A malicious guest runs with 2 vCPUs pinned,
its first vCPU pounds on ICR sending IPIs to the 2nd vCPU

and 2nd vCPU scheduled out forever and not halted
(something that should not happen with Qemu though)

- A normal guest with single vCPU is pinned to run
on the same CPU as the 2nd vCPU of the first guest.

The normal guest continued to run, but was observed to run
about 40% slower.

Therefore AVIC doorbel is strict by default but if the admin
policy is to pin guests and not allow them to share a physical
cpu, then strict doorbel can be set to false and that does
improves the nested (and not nested as well) AVIC perf futher.

Suggestions, comments are welcome.

Best regards,
	Maxim Levitsky

Maxim Levitsky (10):
  KVM: x86: mmu: allow to enable write tracking externally
  x86: KVMGT: use kvm_page_track_write_tracking_enable
  KVM: x86: mmu: add gfn_in_memslot helper
  KVM: x86: mmu: tweak fast path for emulation of access to nested NPT
    pages
  KVM: x86: lapic: don't allow to change APIC ID when apic acceleration
    is enabled
  KVM: x86: SVM: remove avic's broken code that updated APIC ID
  KVM: x86: SVM: move avic state to separate struct
  KVM: x86: rename .set_apic_access_page_addr to reload_apic_access_page
  KVM: nSVM: implement support for nested AVIC
  KVM: SVM: allow to avoid not needed updates to is_running

 arch/x86/include/asm/kvm-x86-ops.h    |   2 +-
 arch/x86/include/asm/kvm_host.h       |   5 +-
 arch/x86/include/asm/kvm_page_track.h |   1 +
 arch/x86/kvm/Kconfig                  |   3 -
 arch/x86/kvm/lapic.c                  |  28 +-
 arch/x86/kvm/mmu.h                    |   8 +-
 arch/x86/kvm/mmu/mmu.c                |  21 +-
 arch/x86/kvm/mmu/page_track.c         |  10 +-
 arch/x86/kvm/svm/avic.c               | 949 ++++++++++++++++++++++++--
 arch/x86/kvm/svm/nested.c             | 131 +++-
 arch/x86/kvm/svm/svm.c                |  31 +-
 arch/x86/kvm/svm/svm.h                | 165 ++++-
 arch/x86/kvm/trace.h                  | 140 +++-
 arch/x86/kvm/vmx/vmx.c                |   8 +-
 arch/x86/kvm/x86.c                    |  17 +-
 drivers/gpu/drm/i915/Kconfig          |   1 -
 drivers/gpu/drm/i915/gvt/kvmgt.c      |   5 +
 include/linux/kvm_host.h              |  10 +-
 18 files changed, 1413 insertions(+), 122 deletions(-)