Re: [PATCH v10 00/27] Enable CET Virtualization

[Sean Christopherson <seanjc@google.com>]

On Sun, Feb 18, 2024, Yang Weijiang wrote:
> Sean Christopherson (4):
>   x86/fpu/xstate: Always preserve non-user xfeatures/flags in
>     __state_perm
>   KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data
>   KVM: x86: Report XSS as to-be-saved if there are supported features
>   KVM: x86: Load guest FPU state when access XSAVE-managed MSRs
> 
> Yang Weijiang (23):
>   x86/fpu/xstate: Refine CET user xstate bit enabling
>   x86/fpu/xstate: Add CET supervisor mode state support
>   x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set
>   x86/fpu/xstate: Introduce fpu_guest_cfg for guest FPU configuration
>   x86/fpu/xstate: Create guest fpstate with guest specific config
>   x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal
>     fpstate
>   KVM: x86: Rename kvm_{g,s}et_msr()* to menifest emulation operations
>   KVM: x86: Refine xsave-managed guest register/MSR reset handling
>   KVM: x86: Add kvm_msr_{read,write}() helpers
>   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: Use KVM-governed feature framework to track "SHSTK/IBT
>     enabled"
>   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: Enable CET virtualization for VMX and advertise to userspace
>   KVM: nVMX: Introduce new VMX_BASIC bit for event error_code delivery
>     to L1
>   KVM: nVMX: Enable CET support for nested guest
>   KVM: x86: Don't emulate instructions guarded by CET

A decent number of comments, but almost all of them are quite minor.  The big
open is how to handle save/restore of SSP from userspace.

Instead of spinning a full v10, maybe send an RFC for KVM_{G,S}ET_ONE_REG idea?
That will make it easier to review, and if you delay v11 a bit, I should be able
to get various series applied that have minor conflicts/dependencies, e.g. the
MSR access and the kvm_host series.