Introduce support for guest CET feature

Control-flow Enforcement Technology (CET) provides protection against Return/Jump-Oriented Programming (ROP/JOP) attack. There're two CET
subfeatures: Shadow Stack (SHSTK) and Indirect Branch Tracking (IBT). SHSTK is to prevent ROP and IBT is to prevent JOP.

Several parts in KVM have been updated to provide guest CET support, including:
CPUID/XSAVES settings, MSR passthrough, user-space MSR access interface, vmentry/vmexit config, nested VM etc. These patches are dependent on CET kernel patches for XSAVES support and CET definitions, e.g., MSR and related feature flags.

CET kernel patches: refer to [1], [2].

Previous CET KVM patches: refer to [3].

CET QEMU patches: refer to [4].

CET KVM unit-test patch: refer to [5].

[1]: CET Shadow Stack patches v18:
https://lkml.kernel.org/linux-api/[email protected]/

[2]: Indirect Branch Tracking patches v18:
https://lkml.kernel.org/linux-api/[email protected]/

[3]: CET KVM patches v14:
https://lkml.kernel.org/kvm/[email protected]/

[4]: CET QEMU patches:
https://patchwork.ozlabs.org/project/qemu-devel/patch/[email protected]/

[5]: CET KVM unit-test patch:
https://patchwork.kernel.org/project/kvm/patch/[email protected]/

Changes in v15:
- Changed patches per Paolo's review feedback on v14.
- Added a new patch for GUEST_SSP save/restore in guest SMM case.
- Fixed guest call-trace issue due to CET MSR interception.
- Removed unnecessary guest CET state cleanup in VMCS.
- Rebased patches to 5.11-rc6.

Sean Christopherson (2):
KVM: x86: Report XSS as an MSR to be saved if there are supported
features
KVM: x86: Load guest fpu state when accessing MSRs managed by XSAVES

Yang Weijiang (12):
KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS
KVM: x86: Add #CP support in guest exception dispatch
KVM: VMX: Introduce CET VMCS fields and flags
KVM: x86: Add fault checks for CR4.CET
KVM: VMX: Emulate reads and writes to CET MSRs
KVM: VMX: Add a synthetic MSR to allow userspace VMM to access
GUEST_SSP
KVM: x86: Report CET MSRs as to-be-saved if CET is supported
KVM: x86: Enable CET virtualization for VMX and advertise CET to
userspace
KVM: VMX: Pass through CET MSRs to the guest when supported
KVM: nVMX: Add helper to check the vmcs01 MSR bitmap for MSR
pass-through
KVM: nVMX: Enable CET support for nested VMX
KVM: x86: Save/Restore GUEST_SSP to/from SMRAM

 arch/x86/include/asm/kvm_host.h      |   4 +-
 arch/x86/include/asm/vmx.h           |   8 ++
 arch/x86/include/uapi/asm/kvm.h      |   1 +
 arch/x86/include/uapi/asm/kvm_para.h |   1 +
 arch/x86/kvm/cpuid.c                 |  26 +++-
 arch/x86/kvm/emulate.c               |  11 ++
 arch/x86/kvm/vmx/capabilities.h      |   5 +
 arch/x86/kvm/vmx/nested.c            |  57 ++++++--
 arch/x86/kvm/vmx/vmcs12.c            |   6 +
 arch/x86/kvm/vmx/vmcs12.h            |  14 +-
 arch/x86/kvm/vmx/vmx.c               | 202 ++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c                   |  67 ++++++++-
 arch/x86/kvm/x86.h                   |  10 +-
 13 files changed, 387 insertions(+), 25 deletions(-)

2.26.2