[PATCH] KVM: arm64: FFA: Release hyp rx buffer

[Vincent Donnefort]

According to the FF-A spec (1.2 BET0 7.2.2.4.2), after a producer has
written into a buffer, it is "full" and now owned by the consumer until
it is read and "empty". This must be signaled by the consumer with the
RX_RELEASE invocation.

It is clear from the spec (7.2.2.4.2), that MEM_RETRIEVE_RESP is
transferring the ownership from producer (in our case SPM) to consumer
(hypervisor). We must then subsequently invoke RX_RELEASE to transfer
back the ownership (i.e. to let SPM mark the buffer as "empty").

It is less clear though what is happening with MEM_FRAG_TX. But this
invocation, as a response to MEM_FRAG_RX writes into the same hypervisor
RX buffer. Also this is matching the TF-A implementation where the RX
buffer is marked "full" during a MEM_FRAG_RX.

Release the RX hypervisor buffer in those two cases. This will unblock
later invocations using this buffer which would otherwise fail.
(RETRIEVE_REQ, MEM_FRAG_RX and PARTITION_INFO_GET).

Signed-off-by: Vincent Donnefort <vdonnefort at google.com>

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 02746f9d0980..efb053af331c 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -177,6 +177,14 @@ static void ffa_retrieve_req(struct arm_smccc_res *res, u32 len)
 			  res);
 }
 
+static void ffa_rx_release(struct arm_smccc_res *res)
+{
+	arm_smccc_1_1_smc(FFA_RX_RELEASE,
+			  0, 0,
+			  0, 0, 0, 0, 0,
+			  res);
+}
+
 static void do_ffa_rxtx_map(struct arm_smccc_res *res,
 			    struct kvm_cpu_context *ctxt)
 {
@@ -543,16 +551,19 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
 	if (WARN_ON(offset > len ||
 		    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) {
 		ret = FFA_RET_ABORTED;
+		ffa_rx_release(res);
 		goto out_unlock;
 	}
 
 	if (len > ffa_desc_buf.len) {
 		ret = FFA_RET_NO_MEMORY;
+		ffa_rx_release(res);
 		goto out_unlock;
 	}
 
 	buf = ffa_desc_buf.buf;
 	memcpy(buf, hyp_buffers.rx, fraglen);
+	ffa_rx_release(res);
 
 	for (fragoff = fraglen; fragoff < len; fragoff += fraglen) {
 		ffa_mem_frag_rx(res, handle_lo, handle_hi, fragoff);
@@ -563,6 +574,7 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
 
 		fraglen = res->a3;
 		memcpy((void *)buf + fragoff, hyp_buffers.rx, fraglen);
+		ffa_rx_release(res);
 	}
 
 	ffa_mem_reclaim(res, handle_lo, handle_hi, flags);

base-commit: 6d69b6c12fce479fde7bc06f686212451688a102
-- 
2.45.1.288.g0e0cd299f1-goog