[PATCH v15 00/41] KVM: x86: Mega-CET

Sean Christopherson
2025-09-12T23:23:25Z

This series is (hopefully) all of the in-flight CET virtualization patches
in one big bundle. Please holler if I missed a patch or three as this is what
I am planning on applying for 6.18 (modulo fixups and whatnot), i.e. if there's
something else that's needed to enable CET virtualization, now's the time...

Patches 1-3 probably need the most attention, as they are new in v15 and I
don't have a fully working SEV-ES setup (don't have the right guest firmware,
ugh). Though testing on everything would be much appreciated.

I kept almost all Tested-by tags even for patches that I massaged a bit, and
only dropped tags for the "don't emulate CET stuff" patch. In theory, the
changes I've made *should* be benign. Please yell, loudly, if I broken
something and/or you want me to drop your Tested-by.

v15:
- Collect reviews (hopefully I got 'em all).
- Add support for KVM_GET_REG_LIST.
- Load FPU when accessing XSTATE MSRs via ONE_REG ioctls.
- Explicitly return -EINVAL on kvm_set_one_msr() failure.
- Make is_xstate_managed_msr() more precise (check guest caps).
- Dedup guts of kvm_{g,s}et_xstate_msr() (as kvm_access_xstate_msr()).
- WARN if KVM uses kvm_access_xstate_msr() to access an MSR that isn't
managed via XSAVE.
- Document why S_CET isn't treated as an XSTATE-managed MSR.
- Mark VMCB_CET as clean/dirty as appropriate.
- Add nSVM support for the CET VMCB fields.
- Add an "msrs" selftest to coverage ONE_REG and host vs. guest accesses in
general.
- Add patches to READ_ONCE() guest-writable GHCB fields, and to check the
validity of XCR0 "writes".
- Check the validity of XSS "writes" via common MSR emulation.
- Add {CP,HV,VC,SV}_VECTOR definitions so that tracing and selftests can
pretty print them.
- Add pretty printing for unexpected exceptions in selftests.
- Tweak the emulator rejection to be more precise (grab S_CET vs. U_CET based
CPL for near transfers), and to avoid unnecessary reads of CR4, S_CET, and
U_CET.

Intel (v14): https://lkml.kernel.org/r/20250909093953.202028-1-chao.gao%40intel.com
AMD (v4): https://lore.kernel.org/all/20250908201750.98824-1-john.allen@amd.com
grsec (v3): https://lkml.kernel.org/r/20250813205957.14135-1-minipli%40grsecurity.net

Chao Gao (4):
KVM: x86: Check XSS validity against guest CPUIDs
KVM: nVMX: Add consistency checks for CR0.WP and CR4.CET
KVM: nVMX: Add consistency checks for CET states
KVM: nVMX: Advertise new VM-Entry/Exit control bits for CET state

John Allen (4):
KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs
KVM: x86: SVM: Update dump_vmcb with shadow stack save area additions
KVM: x86: SVM: Pass through shadow stack MSRs as appropriate
KVM: SVM: Enable shadow stack virtualization for SVM

Mathias Krause (1):
KVM: VMX: Make CR4.CET a guest owned bit

Sean Christopherson (17):
KVM: SEV: Rename kvm_ghcb_get_sw_exit_code() to
kvm_get_cached_sw_exit_code()
KVM: SEV: Read save fields from GHCB exactly once
KVM: SEV: Validate XCR0 provided by guest in GHCB
KVM: x86: Report XSS as to-be-saved if there are supported features
KVM: x86: Load guest FPU state when access XSAVE-managed MSRs
KVM: nSVM: Save/load CET Shadow Stack state to/from vmcb12/vmcb02
KVM: SEV: Synchronize MSR_IA32_XSS from the GHCB when it's valid
KVM: x86: Add human friendly formatting for #XM, and #VE
KVM: x86: Define Control Protection Exception (#CP) vector
KVM: x86: Define AMD's #HV, #VC, and #SX exception vectors
KVM: selftests: Add ex_str() to print human friendly name of exception
vectors
KVM: selftests: Add an MSR test to exercise guest/host and read/write
KVM: selftests: Add support for MSR_IA32_{S,U}_CET to MSRs test
KVM: selftests: Extend MSRs test to validate vCPUs without supported
features
KVM: selftests: Add KVM_{G,S}ET_ONE_REG coverage to MSRs test
KVM: selftests: Add coverate for KVM-defined registers in MSRs test
KVM: selftests: Verify MSRs are (not) in save/restore list when
(un)supported

Yang Weijiang (15):
KVM: x86: Introduce KVM_{G,S}ET_ONE_REG uAPIs support
KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS
KVM: x86: Initialize kvm_caps.supported_xss
KVM: x86: Add fault checks for guest CR4.CET setting
KVM: x86: Report KVM supported CET MSRs as to-be-saved
KVM: VMX: Introduce CET VMCS fields and control bits
KVM: x86: Enable guest SSP read/write interface with new uAPIs
KVM: VMX: Emulate read and write to CET MSRs
KVM: x86: Save and reload SSP to/from SMRAM
KVM: VMX: Set up interception for CET MSRs
KVM: VMX: Set host constant supervisor states to VMCS fields
KVM: x86: Don't emulate instructions affected by CET features
KVM: x86: Enable CET virtualization for VMX and advertise to userspace
KVM: nVMX: Virtualize NO_HW_ERROR_CODE_CC for L1 event injection to L2
KVM: nVMX: Prepare for enabling CET support for nested guest

Documentation/virt/kvm/api.rst | 14 +-
arch/x86/include/asm/kvm_host.h | 6 +-
arch/x86/include/asm/vmx.h | 9 +
arch/x86/include/uapi/asm/kvm.h | 34 ++
arch/x86/kvm/cpuid.c | 17 +-
arch/x86/kvm/emulate.c | 58 ++-
arch/x86/kvm/kvm_cache_regs.h | 3 +-
arch/x86/kvm/smm.c | 8 +
arch/x86/kvm/smm.h | 2 +-
arch/x86/kvm/svm/nested.c | 20 +
arch/x86/kvm/svm/sev.c | 23 +-
arch/x86/kvm/svm/svm.c | 46 +-
arch/x86/kvm/svm/svm.h | 30 +-
arch/x86/kvm/trace.h | 5 +-
arch/x86/kvm/vmx/capabilities.h | 9 +
arch/x86/kvm/vmx/nested.c | 163 ++++++-
arch/x86/kvm/vmx/nested.h | 5 +
arch/x86/kvm/vmx/vmcs12.c | 6 +
arch/x86/kvm/vmx/vmcs12.h | 14 +-
arch/x86/kvm/vmx/vmx.c | 84 +++-
arch/x86/kvm/vmx/vmx.h | 9 +-
arch/x86/kvm/x86.c | 362 +++++++++++++-
arch/x86/kvm/x86.h | 37 ++
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../selftests/kvm/include/x86/processor.h | 2 +
.../testing/selftests/kvm/lib/x86/processor.c | 33 ++
.../selftests/kvm/x86/hyperv_features.c | 16 +-
tools/testing/selftests/kvm/x86/msrs_test.c | 440 ++++++++++++++++++
.../selftests/kvm/x86/vmx_pmu_caps_test.c | 4 +-
.../selftests/kvm/x86/xcr0_cpuid_test.c | 12 +-
30 files changed, 1382 insertions(+), 90 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86/msrs_test.c

base-commit: b33f3c899e27cad5a62b15f9e3724fb5e61378c4
--
2.51.0.384.g4c02a37b29-goog