Re: [PATCH 02/12] KVM: guest_memfd: delay folio_mark_uptodate() until after successful preparation

[Michael Roth]

On Thu, Jul 11, 2024 at 06:27:45PM -0400, Paolo Bonzini wrote:
> The up-to-date flag as is now is not too useful; it tells guest_memfd not
> to overwrite the contents of a folio, but it doesn't say that the page
> is ready to be mapped into the guest.  For encrypted guests, mapping
> a private page requires that the "preparation" phase has succeeded,
> and at the same time the same page cannot be prepared twice.
> 
> So, ensure that folio_mark_uptodate() is only called on a prepared page.  If
> kvm_gmem_prepare_folio() or the post_populate callback fail, the folio
> will not be marked up-to-date; it's not a problem to call clear_highpage()
> again on such a page prior to the next preparation attempt.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Reviewed-by: Michael Roth <michael.roth@xxxxxxx>