Re: [PATCH v5 7/8] KVM: SVM: Add Page modification logging support

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

On Wed, 2026-01-14 at 19:33 +0530, Nikunj A. Dadhania wrote:
> > > @@ -748,12 +748,19 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm,
> > >   						V_NMI_BLOCKING_MASK);
> > >   	}
> > >   
> > > -	/* Copied from vmcb01.  msrpm_base can be overwritten later.  */
> > > +	/* Copied from vmcb01. msrpm_base/nested_ctl can be overwritten later. */
> > >   	vmcb02->control.nested_ctl = vmcb01->control.nested_ctl;
> > >   	vmcb02->control.iopm_base_pa = vmcb01->control.iopm_base_pa;
> > >   	vmcb02->control.msrpm_base_pa = vmcb01->control.msrpm_base_pa;
> > >   	vmcb_mark_dirty(vmcb02, VMCB_PERM_MAP);
> > >   
> > > +	/* Disable PML for nested guest as the A/D update is emulated by MMU */
> > 
> > This comment isn't accurate to me.  I think the key reason is, for L2 if
> > PML enabled the recorded GPA will be L2's GPA, but not L1's.
> > 
> > Please update the comment if a new version is needed?
> 
> How about the below:
> 
> +	/*
> +	 * Disable PML for nested guests. When L2 runs with PML enabled, the
> +	 * CPU logs L2 GPAs rather than L1 GPAs, breaking dirty page tracking
> +	 * for the L0 hypervisor.
> +	 */

LGTM.