KVM: arm64: Introduce KVM_PGTABLE_S2_IDMAP stage 2 flag

Introduce a new stage 2 configuration flag to specify that all mappings
in a given page-table will be identity-mapped, as will be the case for
the host. This allows to introduce sanity checks in the map path and to
avoid programming errors.

Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-34-qperret@google.com

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 55452f4..c3674c4 100644 (file)
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -60,9 +60,11 @@ struct kvm_pgtable_mm_ops {
  * enum kvm_pgtable_stage2_flags - Stage-2 page-table flags.
  * @KVM_PGTABLE_S2_NOFWB:      Don't enforce Normal-WB even if the CPUs have
  *                             ARM64_HAS_STAGE2_FWB.
+ * @KVM_PGTABLE_S2_IDMAP:      Only use identity mappings.
  */
 enum kvm_pgtable_stage2_flags {
        KVM_PGTABLE_S2_NOFWB                    = BIT(0),
+       KVM_PGTABLE_S2_IDMAP                    = BIT(1),
 };
 
 /**

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index b22b486..c37c1dc 100644 (file)
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -760,6 +760,9 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
                .arg            = &map_data,
        };
 
+       if (WARN_ON((pgt->flags & KVM_PGTABLE_S2_IDMAP) && (addr != phys)))
+               return -EINVAL;
+
        ret = stage2_set_prot_attr(pgt, prot, &map_data.attr);
        if (ret)
                return ret;