[v3,3/3] KVM: arm64: Release the ownership of the hyp rx buffer to Trustzone

Commit Message

Sebastian Ene March 18, 2025, 4:25 p.m. UTC

Introduce the release FF-A call to notify Trustzone that the hypervisor
has finished copying the data from the buffer shared with Trustzone to
the non-secure partition.

Reported-by: Andrei Homescu <[e-mail]>
Signed-off-by: Sebastian Ene <[e-mail]>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 9 ++++++---
 include/linux/arm_ffa.h       | 3 +++
 2 files changed, 9 insertions(+), 3 deletions(-)

Patch

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 6df6131f1107..ac898ea6274a 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -749,6 +749,7 @@  static void do_ffa_part_get(struct arm_smccc_res *res,
 	DECLARE_REG(u32, uuid3, ctxt, 4);
 	DECLARE_REG(u32, flags, ctxt, 5);
 	u32 count, partition_sz, copy_sz;
+	struct arm_smccc_res _res;
 
 	hyp_spin_lock(&host_buffers.lock);
 	if (!host_buffers.rx) {
@@ -765,11 +766,11 @@  static void do_ffa_part_get(struct arm_smccc_res *res,
 
 	count = res->a2;
 	if (!count)
-		goto out_unlock;
+		goto release_rx;
 
 	if (hyp_ffa_version > FFA_VERSION_1_0) {
 		/* Get the number of partitions deployed in the system */
-		if (flags & 0x1)
+		if (flags & PARTITION_INFO_GET_RETURN_COUNT_ONLY)
 			goto out_unlock;
 
 		partition_sz  = res->a3;
@@ -781,10 +782,12 @@  static void do_ffa_part_get(struct arm_smccc_res *res,
 	copy_sz = partition_sz * count;
 	if (copy_sz > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
 		ffa_to_smccc_res(res, FFA_RET_ABORTED);
-		goto out_unlock;
+		goto release_rx;
 	}
 
 	memcpy(host_buffers.rx, hyp_buffers.rx, copy_sz);
+release_rx:
+	ffa_rx_release(&_res);
 out_unlock:
 	hyp_spin_unlock(&host_buffers.lock);
 }
diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index 850577edadbc..32e235a2bedf 100644
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -223,6 +223,9 @@  extern const struct bus_type ffa_bus_type;
 /* The FF-A 1.0 partition structure lacks the uuid[4] */
 #define FFA_1_0_PARTITON_INFO_SZ	(8)
 
+/* Return the count of partitions deployed in the system */
+#define PARTITION_INFO_GET_RETURN_COUNT_ONLY	(1)
+
 /* FFA transport related */
 struct ffa_partition_info {
 	u16 id;