On Fri, Oct 23, 2020 at 03:37:12PM +0300, Mike Rapoport wrote: > On Tue, Oct 20, 2020 at 09:18:58AM +0300, Kirill A. Shutemov wrote: > > If the protected memory feature enabled, unmap guest memory from > > kernel's direct mappings. > > > > Migration and KSM is disabled for protected memory as it would require a > > special treatment. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > --- > > include/linux/mm.h | 3 +++ > > mm/huge_memory.c | 8 ++++++++ > > mm/ksm.c | 2 ++ > > mm/memory.c | 12 ++++++++++++ > > mm/rmap.c | 4 ++++ > > virt/lib/mem_protected.c | 21 +++++++++++++++++++++ > > 6 files changed, 50 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index ee274d27e764..74efc51e63f0 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -671,6 +671,9 @@ static inline bool vma_is_kvm_protected(struct vm_area_struct *vma) > > return vma->vm_flags & VM_KVM_PROTECTED; > > } > > > > +void kvm_map_page(struct page *page, int nr_pages); > > +void kvm_unmap_page(struct page *page, int nr_pages); > > This still does not seem right ;-) > > And I still think that map/unmap primitives shoud be a part of the > generic mm rather than exported by KVM. Ya, and going a step further, I suspect it will be cleaner in the long run if the kernel does not automatically map or unmap when converting between private and shared/public memory. Conversions will be rare in a well behaved guest, so exiting to userspace and forcing userspace to do the unmap->map would not be a performance bottleneck. In theory, userspace could also maintain separate pools for private vs. public mappings, though I doubt any VMM will do that in practice.
