xen/arm: ffa: support mapping guest RX/TX buffers

Adds support in the mediator to map and unmap the RX and TX buffers
provided by the guest using the two FF-A functions FFA_RXTX_MAP and
FFA_RXTX_UNMAP.

These buffer are later used to transmit data that cannot be passed in
registers only.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

xen/arch/arm/tee/ffa.c

@@ -74,6 +74,12 @@
  */
 #define FFA_RXTX_PAGE_COUNT             1
 
+/*
+ * Limit the number of pages RX/TX buffers guests can map.
+ * TODO support a larger number.
+ */
+#define FFA_MAX_RXTX_PAGE_COUNT         1
+
 /*
  * Flags and field values used for the MSG_SEND_DIRECT_REQ/RESP:
  * BIT(31): Framework or partition message
@@ -169,6 +175,12 @@ struct ffa_partition_info_1_1 {
 };
 
 struct ffa_ctx {
+    void *rx;
+    const void *tx;
+    struct page_info *rx_pg;
+    struct page_info *tx_pg;
+    /* Number of 4kB pages in each of rx/rx_pg and tx/tx_pg */
+    unsigned int page_count;
     /* FF-A version used by the guest */
     uint32_t guest_vers;
     /*
@@ -176,6 +188,7 @@ struct ffa_ctx {
      * ffa_domain_teardown() to know which SPs need to be signalled.
      */
     uint16_t create_signal_count;
+    bool rx_is_free;
 };
 
 /* Negotiated FF-A version to use with the SPMC */
@@ -371,6 +384,11 @@ 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_error(struct cpu_user_regs *regs, uint32_t error_code)
+{
+    set_regs(regs, FFA_ERROR, 0, error_code, 0, 0, 0, 0, 0);
+}
+
 static void set_regs_success(struct cpu_user_regs *regs, uint32_t w2,
                              uint32_t w3)
 {
@@ -392,6 +410,108 @@ static void handle_version(struct cpu_user_regs *regs)
     set_regs(regs, vers, 0, 0, 0, 0, 0, 0, 0);
 }
 
+static uint32_t handle_rxtx_map(uint32_t fid, register_t tx_addr,
+                                register_t rx_addr, uint32_t page_count)
+{
+    uint32_t ret = FFA_RET_INVALID_PARAMETERS;
+    struct domain *d = current->domain;
+    struct ffa_ctx *ctx = d->arch.tee;
+    struct page_info *tx_pg;
+    struct page_info *rx_pg;
+    p2m_type_t t;
+    void *rx;
+    void *tx;
+
+    if ( !smccc_is_conv_64(fid) )
+    {
+        /*
+         * Calls using the 32-bit calling convention must ignore the upper
+         * 32 bits in the argument registers.
+         */
+        tx_addr &= UINT32_MAX;
+        rx_addr &= UINT32_MAX;
+    }
+
+    if ( page_count > FFA_MAX_RXTX_PAGE_COUNT )
+    {
+        printk(XENLOG_ERR "ffa: RXTX_MAP: error: %u pages requested (limit %u)\n",
+               page_count, FFA_MAX_RXTX_PAGE_COUNT);
+        return FFA_RET_NOT_SUPPORTED;
+    }
+
+    /* Already mapped */
+    if ( ctx->rx )
+        return FFA_RET_DENIED;
+
+    tx_pg = get_page_from_gfn(d, gfn_x(gaddr_to_gfn(tx_addr)), &t, P2M_ALLOC);
+    if ( !tx_pg )
+        return FFA_RET_INVALID_PARAMETERS;
+
+    /* Only normal RW RAM for now */
+    if ( t != p2m_ram_rw )
+        goto err_put_tx_pg;
+
+    rx_pg = get_page_from_gfn(d, gfn_x(gaddr_to_gfn(rx_addr)), &t, P2M_ALLOC);
+    if ( !tx_pg )
+        goto err_put_tx_pg;
+
+    /* Only normal RW RAM for now */
+    if ( t != p2m_ram_rw )
+        goto err_put_rx_pg;
+
+    tx = __map_domain_page_global(tx_pg);
+    if ( !tx )
+        goto err_put_rx_pg;
+
+    rx = __map_domain_page_global(rx_pg);
+    if ( !rx )
+        goto err_unmap_tx;
+
+    ctx->rx = rx;
+    ctx->tx = tx;
+    ctx->rx_pg = rx_pg;
+    ctx->tx_pg = tx_pg;
+    ctx->page_count = page_count;
+    ctx->rx_is_free = true;
+    return FFA_RET_OK;
+
+err_unmap_tx:
+    unmap_domain_page_global(tx);
+err_put_rx_pg:
+    put_page(rx_pg);
+err_put_tx_pg:
+    put_page(tx_pg);
+
+    return ret;
+}
+
+static void rxtx_unmap(struct ffa_ctx *ctx)
+{
+    unmap_domain_page_global(ctx->rx);
+    unmap_domain_page_global(ctx->tx);
+    put_page(ctx->rx_pg);
+    put_page(ctx->tx_pg);
+    ctx->rx = NULL;
+    ctx->tx = NULL;
+    ctx->rx_pg = NULL;
+    ctx->tx_pg = NULL;
+    ctx->page_count = 0;
+    ctx->rx_is_free = false;
+}
+
+static uint32_t handle_rxtx_unmap(void)
+{
+    struct domain *d = current->domain;
+    struct ffa_ctx *ctx = d->arch.tee;
+
+    if ( !ctx->rx )
+        return FFA_RET_INVALID_PARAMETERS;
+
+    rxtx_unmap(ctx);
+
+    return FFA_RET_OK;
+}
+
 static void handle_msg_send_direct_req(struct cpu_user_regs *regs, uint32_t fid)
 {
     struct arm_smccc_1_2_regs arg = { .a0 = fid, };
@@ -448,6 +568,7 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
     uint32_t fid = get_user_reg(regs, 0);
     struct domain *d = current->domain;
     struct ffa_ctx *ctx = d->arch.tee;
+    int e;
 
     if ( !ctx )
         return false;
@@ -460,6 +581,22 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
     case FFA_ID_GET:
         set_regs_success(regs, get_vm_id(d), 0);
         return true;
+    case FFA_RXTX_MAP_32:
+    case FFA_RXTX_MAP_64:
+        e = handle_rxtx_map(fid, get_user_reg(regs, 1), get_user_reg(regs, 2),
+                            get_user_reg(regs, 3));
+        if ( e )
+            set_regs_error(regs, e);
+        else
+            set_regs_success(regs, 0, 0);
+        return true;
+    case FFA_RXTX_UNMAP:
+        e = handle_rxtx_unmap();
+        if ( e )
+            set_regs_error(regs, e);
+        else
+            set_regs_success(regs, 0, 0);
+        return true;
     case FFA_MSG_SEND_DIRECT_REQ_32:
     case FFA_MSG_SEND_DIRECT_REQ_64:
         handle_msg_send_direct_req(regs, fid);
@@ -553,6 +690,9 @@ static int ffa_domain_teardown(struct domain *d)
                    get_vm_id(d), subscr_vm_destroyed[n], res);
     }
 
+    if ( ctx->rx )
+        rxtx_unmap(ctx);
+
     XFREE(d->arch.tee);
 
     return 0;