Re: [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates

[Sean Christopherson]

On Mon, Jul 19, 2021, Brijesh Singh wrote:
> 
> On 7/19/21 2:03 PM, Sean Christopherson wrote:
> > On Mon, Jul 19, 2021, Brijesh Singh wrote:
> > Ah, not firmwrare, gotcha.  But we can still use a helper, e.g. an inner
> > double-underscore helper, __rmp_make_private().
> 
> In that case we are basically passing the all the fields defined in the
> 'struct rmpupdate' as individual arguments.

Yes, but (a) not _all_ fields, (b) it would allow hiding "struct rmpupdate", and
(c) this is much friendlier to readers:

	__rmp_make_private(pfn, gpa, PG_LEVEL_4K, svm->asid, true);

than:

	rmpupdate(&rmpupdate);

For the former, I can see in a single line of code that KVM is creating a 4k
private, immutable guest page.  With the latter, I need to go hunt down all code
that modifies rmpupdate to understand what the code is doing.

> How about something like this:
> 
> * core kernel exports the rmpupdate()
> * the include/linux/sev.h header file defines the helper functions
> 
>   int rmp_make_private(u64 pfn, u64 gpa, int psize, int asid)

I think we'll want s/psize/level, i.e. make it more obvious clear that the input
is PG_LEVEL_*.