KVM: arm64: Add FF-A helpers to share/unshare memory with secure world

Extend pKVM's memory protection code so that we can update the host's
stage-2 page-table to track pages shared with secure world by the host
using FF-A and prevent those pages from being mapped into a guest.

Co-developed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230523101828.7328-6-will@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

1 files changed, 68 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 2e9ec4a2a4a3..e327e94d0e40 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -842,6 +842,13 @@ static int check_share(struct pkvm_mem_share *share)
 	case PKVM_ID_HYP:
 		ret = hyp_ack_share(completer_addr, tx, share->completer_prot);
 		break;
+	case PKVM_ID_FFA:
+		/*
+		 * We only check the host; the secure side will check the other
+		 * end when we forward the FFA call.
+		 */
+		ret = 0;
+		break;
 	default:
 		ret = -EINVAL;
 	}
@@ -870,6 +877,13 @@ static int __do_share(struct pkvm_mem_share *share)
 	case PKVM_ID_HYP:
 		ret = hyp_complete_share(completer_addr, tx, share->completer_prot);
 		break;
+	case PKVM_ID_FFA:
+		/*
+		 * We're not responsible for any secure page-tables, so there's
+		 * nothing to do here.
+		 */
+		ret = 0;
+		break;
 	default:
 		ret = -EINVAL;
 	}
@@ -918,6 +932,10 @@ static int check_unshare(struct pkvm_mem_share *share)
 	case PKVM_ID_HYP:
 		ret = hyp_ack_unshare(completer_addr, tx);
 		break;
+	case PKVM_ID_FFA:
+		/* See check_share() */
+		ret = 0;
+		break;
 	default:
 		ret = -EINVAL;
 	}
@@ -946,6 +964,10 @@ static int __do_unshare(struct pkvm_mem_share *share)
 	case PKVM_ID_HYP:
 		ret = hyp_complete_unshare(completer_addr, tx);
 		break;
+	case PKVM_ID_FFA:
+		/* See __do_share() */
+		ret = 0;
+		break;
 	default:
 		ret = -EINVAL;
 	}
@@ -1235,3 +1257,49 @@ void hyp_unpin_shared_mem(void *from, void *to)
 	hyp_unlock_component();
 	host_unlock_component();
 }
+
+int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages)
+{
+	int ret;
+	struct pkvm_mem_share share = {
+		.tx	= {
+			.nr_pages	= nr_pages,
+			.initiator	= {
+				.id	= PKVM_ID_HOST,
+				.addr	= hyp_pfn_to_phys(pfn),
+			},
+			.completer	= {
+				.id	= PKVM_ID_FFA,
+			},
+		},
+	};
+
+	host_lock_component();
+	ret = do_share(&share);
+	host_unlock_component();
+
+	return ret;
+}
+
+int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages)
+{
+	int ret;
+	struct pkvm_mem_share share = {
+		.tx	= {
+			.nr_pages	= nr_pages,
+			.initiator	= {
+				.id	= PKVM_ID_HOST,
+				.addr	= hyp_pfn_to_phys(pfn),
+			},
+			.completer	= {
+				.id	= PKVM_ID_FFA,
+			},
+		},
+	};
+
+	host_lock_component();
+	ret = do_unshare(&share);
+	host_unlock_component();
+
+	return ret;
+}