[PATCH v3 00/12] KVM: Improve VMware guest support

[Zack Rusin <zack.rusin@broadcom.com>]

This series lets userspace VMMs run unmodified VMware guests on KVM;
VMware Workstation uses it to run on top of KVM.  I'm sorry this
version took a lot longer than I'd have liked, but I think it addresses
all the comments and results in a very nice cleanup for KVM in general.

VMware guests talk to the hypervisor through the "backdoor", a set of
about one hundred commands implemented in VMware's userspace.  Guests
reach it through IN/OUT/INS/OUTS on two I/O ports, which VMware allows
from CPL3 regardless of I/O permissions, through RDPMC on three
pseudo-PMCs, and, on newer guests, through VMCALL/VMMCALL with VMware's
magic value in EAX.  KVM already emulates the I/O-port and pseudo-PMC
interfaces, but only behind a module parameter that applies to every VM
on the host.

Patch 1 makes the pseudo-PMCs honor enable_vmware_backdoor.
Patches 2-4 move VMware code to vmware.{c,h} and add CONFIG_KVM_VMWARE.
Patches 5-7 add a per-VM capability, hypercall exits and nested routing.
Patches 8-12 add CPL3 selftest helpers and tests.

Notes:
 - Paolo asked in v1 for someone with the spec to go through the
   commands; Doug did that in the v1 thread and none needs KVM
   (SGDT/SIDT/SLDT/STR are obsolete with UMIP, GET_VCPU_INFO flags are
   constants on KVM, GETTIME returns host time without the TSC,
   STEALCLOCK is ESX-only).
 - The I/O-port and pseudo-PMC interfaces share one flag, as two parts
   of the legacy backdoor.
 - VMware hypercalls are never claimed from L2, so a Hyper-V L2 TLB
   flush that KVM handles in L0 stays a Hyper-V hypercall.
 - SEV: KVM doesn't intercept #GP, so the flag can't bypass I/O
   permissions there.  Protected-state VMs can't enable hypercall exits,
   and KVM doesn't forward hypercalls from protected vCPUs of legacy
   SEV-ES VMs either.
 - tools/include/uapi is left to the perf sync, per its README.
 - Sean, Paolo: the new MAINTAINERS entry lists Doug and me; do you want
   to be listed as for Hyper-V and Xen?

The series is based on kvm-x86/next.

Testing:
 - every patch builds with GCC and Clang, CONFIG_KVM_VMWARE=y and =n
 - KVM selftests and KVM-unit-tests on Intel and AMD, with and without
   the series, enable_vmware_backdoor=0 and =1: no differences besides
   the new tests
 - a legacy KVM_SEV_ES_INIT guest on bare-metal AMD gets no
   KVM_EXIT_VMWARE
 - Windows 11 with VBS runs under VMware Workstation on the series

Changes since v2:
 - New patch 1: the pseudo-PMCs honor enable_vmware_backdoor
 - Split the first patch into code movement, helpers and Kconfig; all
   code in vmware.{c,h}; CONFIG_KVM_VMWARE depends on KVM_X86 (Sean)
 - kvm_is_vmware_*() predicates with the enabled check inside (Sean)
 - One KVM_CAP_X86_VMWARE with flags in the x86 UAPI header instead of
   three capabilities; flags are one-way and only accepted before vCPU
   creation (Xin, Sean); "_L0" dropped from the nested flag (Sean)
 - No stub for the hypercall handler, no #ifdef plus stub (Sean)
 - struct kvm_vmware_exit in the x86 UAPI header (Sean); the exit now
   carries only mode and CPL, registers go through KVM_SYNC_X86_REGS,
   and exception completion is validated
 - Only L1 hypercalls with VMware's magic are claimed
 - Nested SVM fixed: v2's nested_svm_exit_special() hook never fired
 - Selftests: KUT port (Sean), hypercall, Hyper-V coexistence and
   nested routing tests

v2: https://lore.kernel.org/all/20250422161304.579394-1-zack.rusin@broadcom.com
v1: https://lore.kernel.org/all/20241030033514.1728937-1-zack.rusin@broadcom.com

Zack Rusin (12):
  KVM: x86/pmu: Honor enable_vmware_backdoor for VMware pseudo-PMCs
  KVM: x86: Move VMware backdoor support to separate files
  KVM: x86: Encapsulate VMware backdoor checks
  KVM: x86: Add CONFIG_KVM_VMWARE
  KVM: x86: Add a unified VMware capability
  KVM: x86: Forward VMware hypercalls to userspace
  KVM: x86: Route nested VMware backdoors to KVM
  KVM: selftests: Add helpers to run x86 guest code in user mode
  KVM: selftests: Port VMware backdoor coverage
  KVM: selftests: Test VMware hypercall exits
  KVM: selftests: Test VMware hypercall exits with nested Hyper-V
    flushes
  KVM: selftests: Test nested VMware backdoor routing

 Documentation/virt/kvm/api.rst                | 119 +++++-
 MAINTAINERS                                   |  10 +
 arch/x86/include/asm/kvm_host.h               |  11 +
 arch/x86/include/uapi/asm/kvm.h               |  27 ++
 arch/x86/kvm/Kconfig                          |  12 +
 arch/x86/kvm/Makefile                         |   1 +
 arch/x86/kvm/emulate.c                        |   9 +-
 arch/x86/kvm/pmu.c                            |  41 +-
 arch/x86/kvm/pmu.h                            |   5 -
 arch/x86/kvm/svm/svm.c                        |  12 +-
 arch/x86/kvm/vmware.c                         | 201 +++++++++
 arch/x86/kvm/vmware.h                         | 102 +++++
 arch/x86/kvm/vmx/nested.c                     |   5 +
 arch/x86/kvm/vmx/vmx.c                        |   5 +-
 arch/x86/kvm/x86.c                            |  63 ++-
 arch/x86/kvm/x86.h                            |   2 -
 include/uapi/linux/kvm.h                      |   6 +
 tools/testing/selftests/kvm/Makefile.kvm      |   3 +
 .../selftests/kvm/include/x86/hyperv.h        |  21 +
 .../selftests/kvm/include/x86/processor.h     |   7 +
 .../testing/selftests/kvm/lib/x86/processor.c |  87 ++++
 .../testing/selftests/kvm/x86/hyperv_evmcs.c  |  27 +-
 .../selftests/kvm/x86/hyperv_svm_test.c       |  21 +-
 .../selftests/kvm/x86/vmware_backdoor_test.c  | 272 ++++++++++++
 .../selftests/kvm/x86/vmware_hypercall_test.c | 388 ++++++++++++++++++
 .../kvm/x86/vmware_nested_backdoor_test.c     | 223 ++++++++++
 .../selftests/kvm/x86/xen_vmcall_test.c       |  12 +-
 27 files changed, 1587 insertions(+), 105 deletions(-)
 create mode 100644 arch/x86/kvm/vmware.c
 create mode 100644 arch/x86/kvm/vmware.h
 create mode 100644 tools/testing/selftests/kvm/x86/vmware_backdoor_test.c
 create mode 100644 tools/testing/selftests/kvm/x86/vmware_hypercall_test.c
 create mode 100644 tools/testing/selftests/kvm/x86/vmware_nested_backdoor_test.c


base-commit: c37cd5acfc3762e3fec1bf8418dc1471e3d6297d
-- 
2.53.0