[XEN PATCH v7 09/20] xen/arm: ffa: add support for FFA_ID_GET

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Adds support for the FF-A function FFA_ID_GET to return the ID of the
calling client.

Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
---
 xen/arch/arm/tee/ffa.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
index 8b0b80ce1ff5..463fd7730573 100644
--- a/xen/arch/arm/tee/ffa.c
+++ b/xen/arch/arm/tee/ffa.c
@@ -167,6 +167,12 @@ static bool ffa_get_version(uint32_t *vers)
     return true;
 }
 
+static uint16_t get_vm_id(const struct domain *d)
+{
+    /* +1 since 0 is reserved for the hypervisor in FF-A */
+    return d->domain_id + 1;
+}
+
 static void set_regs(struct cpu_user_regs *regs, register_t v0, register_t v1,
                      register_t v2, register_t v3, register_t v4, register_t 
v5,
                      register_t v6, register_t v7)
@@ -181,6 +187,12 @@ static void set_regs(struct cpu_user_regs *regs, 
register_t v0, register_t v1,
         set_user_reg(regs, 7, v7);
 }
 
+static void set_regs_success(struct cpu_user_regs *regs, uint32_t w2,
+                             uint32_t w3)
+{
+    set_regs(regs, FFA_SUCCESS_32, 0, w2, w3, 0, 0, 0, 0);
+}
+
 static void handle_version(struct cpu_user_regs *regs)
 {
     struct domain *d = current->domain;
@@ -210,6 +222,9 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
     case FFA_VERSION:
         handle_version(regs);
         return true;
+    case FFA_ID_GET:
+        set_regs_success(regs, get_vm_id(d), 0);
+        return true;
 
     default:
         gprintk(XENLOG_ERR, "ffa: unhandled fid 0x%x\n", fid);
@@ -221,7 +236,11 @@ static int ffa_domain_init(struct domain *d)
 {
     struct ffa_ctx *ctx;
 
-    if ( !ffa_version )
+     /*
+      * We can't use that last possible domain ID or get_vm_id() would cause
+      * an overflow.
+      */
+    if ( !ffa_version || d->domain_id == UINT16_MAX)
         return -ENODEV;
 
     ctx = xzalloc(struct ffa_ctx);
-- 
2.34.1