Hyper-V nested virt enlightenments for SVM

This patch series enables the nested virtualization enlightenments for SVM. This is very similar to the enlightenments for VMX except for the fact that there is no enlightened VMCS. For SVM, VMCB is already an architectural in-memory data structure.

Note: v5 is just a rebase on hyperv-next(5.13-rc1) and needed a rework based on the patch series: (KVM: VMX: Clean up Hyper-V PV TLB flush)
https://lore.kernel.org/lkml/[email protected]/

The supported enlightenments are:

Enlightened TLB Flush: If this is enabled, ASID invalidations invalidate only gva -> hpa entries. To flush entries derived from NPT, hyper-v provided hypercalls (HvFlushGuestPhysicalAddressSpace or HvFlushGuestPhysicalAddressList) should be used.

Enlightened MSR bitmap(TLFS 16.5.3): "When enabled, L0 hypervisor does not monitor the MSR bitmaps for changes. Instead, the L1 hypervisor must invalidate the corresponding clean field after making changes to one of the MSR bitmaps."

Direct Virtual Flush(TLFS 16.8): The hypervisor exposes hypercalls (HvFlushVirtualAddressSpace, HvFlushVirtualAddressSpaceEx, HvFlushVirtualAddressList, and HvFlushVirtualAddressListEx) that allow operating systems to more efficiently manage the virtual TLB. The L1 hypervisor can choose to allow its guest to use those hypercalls and delegate the responsibility to handle them to the L0 hypervisor. This requires the use of a partition assist page."

L2 Windows boot time was measured with and without the patch. Time was measured from power on to the login screen and was averaged over a consecutive 5 trials:
Without the patch: 42 seconds
With the patch: 29 seconds
--

Changes from v4
- Rebased on top of 5.13-rc1 and reworked based on the changes in the patch series: (KVM: VMX: Clean up Hyper-V PV TLB flush)

Changes from v3
- Included definitions for software/hypervisor reserved fields in SVM architectural data structures.
- Consolidated Hyper-V specific code into svm_onhyperv.[ch] to reduce the "ifdefs". This change applies only to SVM, VMX is not touched and is not in the scope of this patch series.

Changes from v2:
- Refactored the Remote TLB Flush logic into separate hyperv specific source files (kvm_onhyperv.[ch]).
- Reverted the VMCB Clean bits macro changes as it is no longer needed.

Changes from v1:
- Move the remote TLB flush related fields from kvm_vcpu_hv and kvm_hv to kvm_vcpu_arch and kvm_arch.
- Modify the VMCB clean mask runtime based on whether L1 hypervisor is running on Hyper-V or not.
- Detect Hyper-V nested enlightenments based on HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS.
- Address other minor review comments.
---

Vineeth Pillai (7):
hyperv: Detect Nested virtualization support for SVM
hyperv: SVM enlightened TLB flush support flag
KVM: x86: hyper-v: Move the remote TLB flush logic out of vmx
KVM: SVM: Software reserved fields
KVM: SVM: hyper-v: Remote TLB flush for SVM
KVM: SVM: hyper-v: Enlightened MSR-Bitmap support
KVM: SVM: hyper-v: Direct Virtual Flush support

 arch/x86/include/asm/hyperv-tlfs.h |   9 ++
 arch/x86/include/asm/kvm_host.h    |   9 ++
 arch/x86/include/asm/svm.h         |   9 +-
 arch/x86/include/uapi/asm/svm.h    |   3 +
 arch/x86/kernel/cpu/mshyperv.c     |  10 ++-
 arch/x86/kvm/Makefile              |   9 ++
 arch/x86/kvm/kvm_onhyperv.c        |  93 +++++++++++++++++++++
 arch/x86/kvm/kvm_onhyperv.h        |  32 +++++++
 arch/x86/kvm/svm/svm.c             |  14 ++++
 arch/x86/kvm/svm/svm.h             |  22 ++++-
 arch/x86/kvm/svm/svm_onhyperv.c    |  41 +++++++++
 arch/x86/kvm/svm/svm_onhyperv.h    | 129 +++++++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.c             | 105 +----------------------
 arch/x86/kvm/vmx/vmx.h             |   9 --
 arch/x86/kvm/x86.c                 |   9 ++
 15 files changed, 384 insertions(+), 119 deletions(-)
 create mode 100644 arch/x86/kvm/kvm_onhyperv.c
 create mode 100644 arch/x86/kvm/kvm_onhyperv.h
 create mode 100644 arch/x86/kvm/svm/svm_onhyperv.c
 create mode 100644 arch/x86/kvm/svm/svm_onhyperv.h

2.25.1