Re: [v4 2/5] KVM: PPC: Book3S HV: track the state GFNs associated with secure VMs

[Ram Pai <linuxram@us.ibm.com>]

On Thu, Jul 23, 2020 at 10:18:30AM +0530, Bharata B Rao wrote:
> On Fri, Jul 17, 2020 at 01:00:24AM -0700, Ram Pai wrote:
> >  	pvt->gpa = gpa;
..snip..
> >  	pvt->kvm = kvm;
> > @@ -524,6 +663,7 @@ static unsigned long kvmppc_share_page(struct kvm *kvm, unsigned long gpa,
> >  		uvmem_page = pfn_to_page(uvmem_pfn);
> >  		pvt = uvmem_page->zone_device_data;
> >  		pvt->skip_page_out = true;
> > +		pvt->remove_gfn = false;
> >  	}
> >  
> >  retry:
> > @@ -537,12 +677,16 @@ static unsigned long kvmppc_share_page(struct kvm *kvm, unsigned long gpa,
> >  		uvmem_page = pfn_to_page(uvmem_pfn);
> >  		pvt = uvmem_page->zone_device_data;
> >  		pvt->skip_page_out = true;
> > +		pvt->remove_gfn = false;
> 
> This is the case of making an already secure page as shared page.
> A comment here as to why remove_gfn is set to false here will help.
> 
> Also isn't it by default false? Is there a situation where it starts
> out by default false, becomes true later and you are required to
> explicitly mark it false here?

It is by default false. And will be true when the GFN is
released/invalidated through kvmppc_uvmem_drop_pages().

It is marked false explicitly here, just to be safe, and protect
against any implicit changes.

> 
> Otherwise, Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>
> 
Thanks for the review.

RP