On Wed, 8 Dec 2021 at 09:51, Quentin Perret <qperret@xxxxxxxxxx> wrote: > > Hi Andrew, > > On Tuesday 07 Dec 2021 at 14:47:14 (+0000), Andrew Walbran wrote: > > On Wed, 1 Dec 2021 at 17:04, 'Quentin Perret' via kernel-team > > <kernel-team@xxxxxxxxxxx> wrote: > > > > > > From: Will Deacon <will@xxxxxxxxxx> > > > > > > Implement kvm_pgtable_hyp_unmap() which can be used to remove hypervisor > > > stage-1 mappings at EL2. > > > > > > Signed-off-by: Will Deacon <will@xxxxxxxxxx> > > > Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx> > > > --- > > > arch/arm64/include/asm/kvm_pgtable.h | 21 ++++++++++ > > > arch/arm64/kvm/hyp/pgtable.c | 63 ++++++++++++++++++++++++++++ > > > 2 files changed, 84 insertions(+) > > > > > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > > > index 027783829584..9d076f36401d 100644 > > > --- a/arch/arm64/include/asm/kvm_pgtable.h > > > +++ b/arch/arm64/include/asm/kvm_pgtable.h > > > @@ -251,6 +251,27 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt); > > > int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys, > > > enum kvm_pgtable_prot prot); > > > > > > +/** > > > + * kvm_pgtable_hyp_unmap() - Remove a mapping from a hypervisor stage-1 page-table. > > > + * @pgt: Page-table structure initialised by kvm_pgtable_hyp_init(). > > > + * @addr: Virtual address from which to remove the mapping. > > > + * @size: Size of the mapping. > > > + * > > > + * The offset of @addr within a page is ignored, @size is rounded-up to > > > + * the next page boundary and @phys is rounded-down to the previous page > > > + * boundary. > > > + * > > > + * TLB invalidation is performed for each page-table entry cleared during the > > > + * unmapping operation and the reference count for the page-table page > > > + * containing the cleared entry is decremented, with unreferenced pages being > > > + * freed. The unmapping operation will stop early if it encounters either an > > > + * invalid page-table entry or a valid block mapping which maps beyond the range > > > + * being unmapped. > > > > How is the caller expected to break up the block mapping? Why not > > handle that within this function? > > We don't really use block mappings for the hyp stage-1, since pretty > much forever (see the loop in pkvm_create_mappings_locked() for ex), so > handling it here would be somewhat unnecessary complexity. Handling this > in the pgtable code itself (which I assume would mean proactively > re-mapping the rest of the range with page-granularity mappings or > something along those lines) is tricky because of BBM and concurrency, > so I'd rather avoid handling same-level aborts at EL2 and all that mess > unless we have a good reason. Is there a use-case where you think that'd > be needed? Aha, I didn't realise that block mappings, but it makes sense in that case. How about adding a note to the function comment here explaining that reasoning? Otherwise it sounds like the caller has to handle it somehow. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
