[PATCH v7 31/45] arm64: rme: Prevent Device mappings for Realms

[Steven Price]

Physical device assignment is not yet supported by the RMM, 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@xxxxxxx>
---
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 8c656a0ef4e9..a849ff66e584 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1173,6 +1173,10 @@ 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;
 
@@ -1763,6 +1767,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (exec_fault && device)
 		return -ENOEXEC;
 
+	/*
+	 * 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;
+
 	/*
 	 * Potentially reduce shadow S2 permissions to match the guest's own
 	 * S2. For exec faults, we'd only reach this point if the guest
-- 
2.43.0