On Mon, Mar 15, 2021 at 04:53:18PM +0000, Quentin Perret wrote: > On Monday 15 Mar 2021 at 16:36:19 (+0000), Will Deacon wrote: > > On Mon, Mar 15, 2021 at 02:35:29PM +0000, Quentin Perret wrote: > > > As the host stage 2 will be identity mapped, all the .hyp memory regions > > > and/or memory pages donated to protected guestis will have to marked > > > invalid in the host stage 2 page-table. At the same time, the hypervisor > > > will need a way to track the ownership of each physical page to ensure > > > memory sharing or donation between entities (host, guests, hypervisor) is > > > legal. > > > > > > In order to enable this tracking at EL2, let's use the host stage 2 > > > page-table itself. The idea is to use the top bits of invalid mappings > > > to store the unique identifier of the page owner. The page-table owner > > > (the host) gets identifier 0 such that, at boot time, it owns the entire > > > IPA space as the pgd starts zeroed. > > > > > > Provide kvm_pgtable_stage2_set_owner() which allows to modify the > > > ownership of pages in the host stage 2. It re-uses most of the map() > > > logic, but ends up creating invalid mappings instead. This impacts > > > how we do refcount as we now need to count invalid mappings when they > > > are used for ownership tracking. > > > > > > Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx> > > > --- > > > arch/arm64/include/asm/kvm_pgtable.h | 21 +++++ > > > arch/arm64/kvm/hyp/pgtable.c | 127 ++++++++++++++++++++++----- > > > 2 files changed, 124 insertions(+), 24 deletions(-) > > > > > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > > > index 4ae19247837b..683e96abdc24 100644 > > > --- a/arch/arm64/include/asm/kvm_pgtable.h > > > +++ b/arch/arm64/include/asm/kvm_pgtable.h > > > @@ -238,6 +238,27 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, > > > u64 phys, enum kvm_pgtable_prot prot, > > > void *mc); > > > > > > +/** > > > + * kvm_pgtable_stage2_set_owner() - Annotate invalid mappings with metadata > > > + * encoding the ownership of a page in the > > > + * IPA space. > > > > The function does more than this, though, as it will also go ahead and unmap > > existing valid mappings which I think should be mentioned here, no? > > Right, I see why you mean. How about: > > 'Unmap and annotate pages in the IPA space to track ownership' I think I'd go with: 'Unmap pages and annotate the invalid mappings with ownership metadata for the unmapped IPA range.' as it's the page-table which is annotated, not the actual pages (which could potentially be mapped by other page-tables). Will _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
