[RFC PATCH 3/4] xen/arm: ffa: Add indirect message between VM

[Bertrand Marquis <bertrand.marquis@xxxxxxx>]

Add support for indirect messages between VMs.
This is only enabled if CONFIG_FFA_VM_TO_VM is selected.

Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
 xen/arch/arm/tee/ffa_msg.c | 96 ++++++++++++++++++++++++++++++++++----
 1 file changed, 88 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/tee/ffa_msg.c b/xen/arch/arm/tee/ffa_msg.c
index 335f246ba657..25f184a06546 100644
--- a/xen/arch/arm/tee/ffa_msg.c
+++ b/xen/arch/arm/tee/ffa_msg.c
@@ -95,9 +95,12 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
     const struct ffa_part_msg_rxtx *src_msg;
     uint16_t dst_id, src_id;
     int32_t ret;
-
-    if ( !ffa_fw_supports_fid(FFA_MSG_SEND2) )
-        return FFA_RET_NOT_SUPPORTED;
+#ifdef CONFIG_FFA_VM_TO_VM
+    struct domain *dst_d;
+    struct ffa_ctx *dst_ctx;
+    struct ffa_part_msg_rxtx *dst_msg;
+    int err;
+#endif
 
     if ( !spin_trylock(&src_ctx->tx_lock) )
         return FFA_RET_BUSY;
@@ -106,10 +109,10 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
     src_id = src_msg->send_recv_id >> 16;
     dst_id = src_msg->send_recv_id & GENMASK(15,0);
 
-    if ( src_id != ffa_get_vm_id(src_d) || !FFA_ID_IS_SECURE(dst_id) )
+    if ( src_id != ffa_get_vm_id(src_d) )
     {
         ret = FFA_RET_INVALID_PARAMETERS;
-        goto out_unlock_tx;
+        goto out;
     }
 
     /* check source message fits in buffer */
@@ -118,12 +121,89 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
          src_msg->msg_offset < sizeof(struct ffa_part_msg_rxtx) )
     {
         ret = FFA_RET_INVALID_PARAMETERS;
-        goto out_unlock_tx;
+        goto out;
     }
 
-    ret = ffa_simple_call(FFA_MSG_SEND2, ((uint32_t)src_id) << 16, 0, 0, 0);
+    if ( FFA_ID_IS_SECURE(dst_id) )
+    {
+        /* Message for a secure partition */
+        if ( !ffa_fw_supports_fid(FFA_MSG_SEND2) )
+        {
+            ret = FFA_RET_NOT_SUPPORTED;
+            goto out;
+        }
+
+        ret = ffa_simple_call(FFA_MSG_SEND2, ((uint32_t)src_id) << 16, 0, 0,
+                              0);
+        goto out;
+    }
 
-out_unlock_tx:
+#ifndef CONFIG_FFA_VM_TO_VM
+    ret = FFA_RET_INVALID_PARAMETERS;
+#else
+    /* Message for a VM */
+    if ( dst_id == 0 )
+    {
+        /* FF-A ID 0 is the hypervisor, this is not valid */
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out;
+    }
+
+    /* This is also checking that dest is not src */
+    err = rcu_lock_live_remote_domain_by_id(dst_id - 1, &dst_d);
+    if ( err )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out;
+    }
+
+    if ( dst_d->arch.tee == NULL )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out_unlock;
+    }
+
+    dst_ctx = dst_d->arch.tee;
+    if ( !dst_ctx->guest_vers )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out_unlock;
+    }
+
+    /* This also checks that destination has set a Rx buffer */
+    ret = ffa_rx_acquire(dst_d);
+    if ( ret )
+        goto out_unlock;
+
+    /* we need to have enough space in the destination buffer */
+    if ( dst_ctx->page_count * FFA_PAGE_SIZE <
+            (sizeof(struct ffa_part_msg_rxtx) + src_msg->msg_size) )
+    {
+        ret = FFA_RET_NO_MEMORY;
+        ffa_rx_release(dst_d);
+        goto out_unlock;
+    }
+
+    dst_msg = dst_ctx->rx;
+
+    /* prepare destination header */
+    dst_msg->flags = 0;
+    dst_msg->reserved = 0;
+    dst_msg->msg_offset = sizeof(struct ffa_part_msg_rxtx);
+    dst_msg->send_recv_id = src_msg->send_recv_id;
+    dst_msg->msg_size = src_msg->msg_size;
+
+    memcpy(dst_ctx->rx + sizeof(struct ffa_part_msg_rxtx),
+           src_ctx->tx + src_msg->msg_offset, src_msg->msg_size);
+
+    /* receiver rx buffer will be released by the receiver*/
+
+out_unlock:
+    rcu_unlock_domain(dst_d);
+    if ( !ret )
+        ffa_raise_rx_buffer_full(dst_d);
+#endif
+out:
     spin_unlock(&src_ctx->tx_lock);
     return ret;
 }
-- 
2.47.0