[PATCH v13 37/48] arm64: RMI: Prevent Device mappings for Realms

Steven Price
2026-03-18T15:56:40Z

Physical device assignment is not supported by RMM v1.0, so it
doesn't make much sense to allow device mappings within the realm.
Prevent them when the guest is a realm.

Signed-off-by: Steven Price <steven.price@arm.com>
---
Changes from v6:
* Fix the check in user_mem_abort() to prevent all pages that are not
guest_memfd() from being mapped into the protected half of the IPA.
Changes from v5:
* Also prevent accesses in user_mem_abort()
---
arch/arm64/kvm/mmu.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index ad1300f366df..7d7caab8f573 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1222,6 +1222,10 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
if (is_protected_kvm_enabled())
return -EPERM;

+ /* We don't support mapping special pages into a Realm */
+ if (kvm_is_realm(kvm))
+ return -EPERM;
+
size += offset_in_page(guest_ipa);
guest_ipa &= PAGE_MASK;

@@ -1965,6 +1969,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
return 1;
}

+ /*
+ * For now we shouldn't be hitting protected addresses because they are
+ * handled in private_memslot_fault(). In the future this check may be
+ * relaxed to support e.g. protected devices.
+ */
+ if (vcpu_is_rec(vcpu) &&
+ kvm_gpa_from_fault(kvm, fault_ipa) == fault_ipa)
+ return -EINVAL;
+
if (nested)
adjust_nested_fault_perms(nested, &prot, &writable);

--
2.43.0