linux-kernel - Re: [PATCH v18 004/121] KVM: VMX: Move out vmx_x86

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Date: Wed, 31 Jan 2024 22:34:19 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: isaku.yamahata@...el.com, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
 erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
 Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
 chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
 Sean Christopherson <sean.j.christopherson@...el.com>,
 Binbin Wu <binbin.wu@...ux.intel.com>
Subject: Re: [PATCH v18 004/121] KVM: VMX: Move out vmx_x86_ops to 'main.c' to
 wrap VMX and TDX

On 1/23/2024 7:52 AM, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> 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@...el.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
> Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>

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