Re: [PATCH v4 4/7] KVM: x86: Move nested CPU dirty logging logic to common code

["Huang, Kai" <kai.huang@intel.com>]

> 
> I have something like this as a separate patch in my stack:
> 
> From 21c3b91ad53dfc2682c01663fe65d60c9424318d Mon Sep 17 00:00:00 2001
> From: Nikunj A Dadhania <nikunj@amd.com>
> Date: Tue, 30 Sep 2025 05:10:15 +0000
> Subject: [PATCH] KVM: VMX: Use cpu_dirty_log_size instead of enable_pml for
>  PML checks
> 
> Replace the enable_pml check with cpu_dirty_log_size in VMX PML code
> to determine whether PML is enabled on a per-VM basis. The enable_pml
> module parameter is a global setting that doesn't reflect per-VM
> capabilities, whereas cpu_dirty_log_size accurately indicates whether
> a specific VM has PML enabled.
> 
> For example, TDX VMs don't yet support PML. Using cpu_dirty_log_size
> ensures the check correctly reflects this, while enable_pml would
> incorrectly indicate PML is available.
> 
> This also improves consistency with kvm_mmu_update_cpu_dirty_logging(),
> which already uses cpu_dirty_log_size to determine PML enablement.

I would add this is a preparation for moving this code out to x86 common
to share with AMD PML.  Otherwise it's not a mandatory change, albeit it
is slightly better in terms of code consistency.

> 
> Suggested-by: Kai Huang <kai.huang@intel.com>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>

Thanks for doing this:

Reviewed-by: Kai Huang <kai.huang@intel.com>

> ---
>  arch/x86/kvm/vmx/vmx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index aa1ba8db6392..9e0c0e29d47e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -8199,7 +8199,7 @@ void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  
> -	if (WARN_ON_ONCE(!enable_pml))
> +	if (WARN_ON_ONCE(!vcpu->kvm->arch.cpu_dirty_log_size))
>  		return;
>  
>  	if (is_guest_mode(vcpu)) {