[PATCH v6 6/9] xen/arm: ffa: support mapping guest RX/TX buffers

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

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 to transmit data that cannot be passed in
registers only.

Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
---
 xen/arch/arm/ffa.c | 131 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 129 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/ffa.c b/xen/arch/arm/ffa.c
index 1e94113b20bd..60157a696a9a 100644
--- a/xen/arch/arm/ffa.c
+++ b/xen/arch/arm/ffa.c
@@ -196,10 +196,17 @@ struct ffa_partition_info_1_1 {
 };
 
 struct ffa_ctx {
+    void *rx;
+    const void *tx;
+    struct page_info *rx_pg;
+    struct page_info *tx_pg;
+    unsigned int page_count;
     uint32_t guest_vers;
+    bool tx_is_mine;
     bool interrupted;
 };
 
+
 /* Negotiated FF-A version to use with the SPMC */
 static uint32_t ffa_version __ro_after_init;
 
@@ -384,6 +391,11 @@ 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)
 {
@@ -405,6 +417,99 @@ 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.ffa;
+    struct page_info *tx_pg;
+    struct page_info *rx_pg;
+    p2m_type_t t;
+    void *rx;
+    void *tx;
+
+    if ( !smccc_is_conv_64(fid) )
+    {
+        tx_addr &= UINT32_MAX;
+        rx_addr &= UINT32_MAX;
+    }
+
+    /* For now to keep things simple, only deal with a single page */
+    if ( page_count != 1 )
+        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 RAM for now */
+    if ( !p2m_is_ram(t) )
+        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 RAM for now */
+    if ( !p2m_is_ram(t) )
+        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 = 1;
+    ctx->tx_is_mine = 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->tx_is_mine = false;
+}
+
+static uint32_t handle_rxtx_unmap(void)
+{
+    struct domain *d = current->domain;
+    struct ffa_ctx *ctx = d->arch.ffa;
+
+    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, };
@@ -469,6 +574,7 @@ bool ffa_handle_call(struct cpu_user_regs *regs, uint32_t 
fid)
 {
     struct domain *d = current->domain;
     struct ffa_ctx *ctx = d->arch.ffa;
+    int e;
 
     if ( !ctx )
         return false;
@@ -481,6 +587,24 @@ bool ffa_handle_call(struct cpu_user_regs *regs, uint32_t 
fid)
     case FFA_ID_GET:
         set_regs_success(regs, get_vm_id(d), 0);
         return true;
+    case FFA_RXTX_MAP_32:
+#ifdef CONFIG_ARM_64
+    case FFA_RXTX_MAP_64:
+#endif
+        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:
 #ifdef CONFIG_ARM_64
     case FFA_MSG_SEND_DIRECT_REQ_64:
@@ -501,8 +625,8 @@ uint32_t ffa_get_call_count(void)
     if ( IS_ENABLED(CONFIG_FFA) )
     {
         if ( IS_ENABLED(CONFIG_ARM_64) )
-            count += 1;
-        count += 3;
+            count += 2;
+        count += 5;
     }
 
     return count;
@@ -571,6 +695,9 @@ void ffa_domain_destroy(struct domain *d)
                    get_vm_id(d), subscr_vm_destroyed[n], res);
     }
 
+    if ( ctx->rx )
+        rxtx_unmap(ctx);
+
     XFREE(d->arch.ffa);
 }
 
-- 
2.31.1