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

[Brijesh Singh]

On 7/19/21 2:03 PM, Sean Christopherson wrote:
> On Mon, Jul 19, 2021, Brijesh Singh wrote:
> > On 7/19/21 12:18 PM, Sean Christopherson wrote:
> > > > Okay, I will add helper to make things easier. One case where we will
> > > > need to directly call the rmpupdate() is during the LAUNCH_UPDATE
> > > > command. In that case the page is private and its immutable bit is also
> > > > set. This is because the firmware makes change to the page, and we are
> > > > required to set the immutable bit before the call.
> > >
> > > Or do "int rmp_make_firmware(u64 pfn, bool immutable)"?
> >
> > That's not what we need.
> >
> > We need 'rmp_make_private() + immutable' all in one RMPUPDATE.  Here is the
> > snippet from SNP_LAUNCH_UPDATE.
>
> 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. 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)
  int rmp_make_firmware(u64 pfn, int psize);
  int rmp_make_shared(u64 pfn, int psize);

In most of the case above 3 helpers are good. If driver finds that the 
above helper does not fit its need (such as SNP_LAUNCH_UPDATE) then call 
the rmpupdate() without going through the helper.

-Brijesh