Re: [PATCH v18 004/121] KVM: VMX: Move out vmx_x86_ops to 'main.c' to wrap VMX and TDX

[Xiaoyao Li]

On 1/23/2024 7:52 AM, isaku.yamahata@xxxxxxxxx wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> KVM accesses Virtual Machine Control Structure (VMCS) with VMX instructions
> to operate on VM.  TDX doesn't allow VMM to operate VMCS directly.
> Instead, TDX has its own data structures, and TDX SEAMCALL APIs for VMM to
> indirectly operate those data structures.  This means we must have a TDX
> version of kvm_x86_ops.
>
> The existing global struct kvm_x86_ops already defines an interface which
> fits with TDX.  But kvm_x86_ops is system-wide, not per-VM structure.  To
> allow VMX to coexist with TDs, the kvm_x86_ops callbacks will have wrappers
> "if (tdx) tdx_op() else vmx_op()" to switch VMX or TDX at run time.
>
> To split the runtime switch, the VMX implementation, and the TDX
> implementation, add main.c, and move out the vmx_x86_ops hooks in
> preparation for adding TDX, which can coexist with VMX, i.e. KVM can run
> both VMs and TDs.  Use 'vt' for the naming scheme as a nod to VT-x and as a
> concatenation of VmxTdx.
>
> The current code looks as follows.
> In vmx.c
>    static vmx_op() { ... }
>    static struct kvm_x86_ops vmx_x86_ops = {
>          .op = vmx_op,
>    initialization code
>
> The eventually converted code will look like
> In vmx.c, keep the VMX operations.
>    vmx_op() { ... }
>    VMX initialization
> In tdx.c, define the TDX operations.
>    tdx_op() { ... }
>    TDX initialization
> In x86_ops.h, declare the VMX and TDX operations.
>    vmx_op();
>    tdx_op();
> In main.c, define common wrappers for VMX and TDX.
>    static vt_ops() { if (tdx) tdx_ops() else vmx_ops() }
>    static struct kvm_x86_ops vt_x86_ops = {
>          .op = vt_op,
>    initialization to call VMX and TDX initialization
>
> Opportunistically, fix the name inconsistency from vmx_create_vcpu() and
> vmx_free_vcpu() to vmx_vcpu_create() and vmx_vcpu_free().
>
> Co-developed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>