Re: [PATCH 03/21] KVM: x86/mmu: Do not enable page track for TD guest

[Paolo Bonzini]

On 9/4/24 05:07, Rick Edgecombe wrote:
> From: Yan Zhao <yan.y.zhao@xxxxxxxxx>
>
> TDX does not support write protection and hence page track.
> Though !tdp_enabled and kvm_shadow_root_allocated(kvm) are always false
> for TD guest, should also return false when external write tracking is
> enabled.
>
> Cc: Yuan Yao <yuan.yao@xxxxxxxxxxxxxxx>
> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
> ---
> v19:
> - drop TDX: from the short log
> - Added reviewed-by: BinBin
> ---
>   arch/x86/kvm/mmu/page_track.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> index 561c331fd6ec..26436113103a 100644
> --- a/arch/x86/kvm/mmu/page_track.c
> +++ b/arch/x86/kvm/mmu/page_track.c
> @@ -35,6 +35,9 @@ static bool kvm_external_write_tracking_enabled(struct kvm *kvm)
>   
>   bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
>   {
> +	if (kvm->arch.vm_type == KVM_X86_TDX_VM)
> +		return false;
> +
>   	return kvm_external_write_tracking_enabled(kvm) ||
>   	       kvm_shadow_root_allocated(kvm) || !tdp_enabled;
>   }

You should instead return an error from 
kvm_enable_external_write_tracking().

This will cause kvm_page_track_register_notifier() and therefore 
intel_vgpu_open_device() to fail.

Paolo