[undi] Align the received frame payload for faster processing

The undinet driver always has to make a copy of the received frame
into an I/O buffer.  Align this copy sensibly so that subsequent
operations are as fast as possible.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/arch/i386/drivers/net/undinet.c b/src/arch/i386/drivers/net/undinet.c
index 190144156c42ea6646df9c229a9d0fc50d912cb0..def44113d7d49237ebe72fede1ed00919b51a4b3 100644 (file)
--- a/src/arch/i386/drivers/net/undinet.c
+++ b/src/arch/i386/drivers/net/undinet.c
@@ -70,6 +70,9 @@ struct undi_nic {
 /** Delay between retries of PXENV_UNDI_INITIALIZE */
 #define UNDI_INITIALIZE_RETRY_DELAY_MS 200
 
+/** Alignment of received frame payload */
+#define UNDI_RX_ALIGN 16
+
 static void undinet_close ( struct net_device *netdev );
 
 /** Address of UNDI entry point */
@@ -299,6 +302,7 @@ static void undinet_poll ( struct net_device *netdev ) {
        struct s_PXENV_UNDI_ISR undi_isr;
        struct io_buffer *iobuf = NULL;
        size_t len;
+       size_t reserve_len;
        size_t frag_len;
        size_t max_frag_len;
        int rc;
@@ -346,6 +350,8 @@ static void undinet_poll ( struct net_device *netdev ) {
                        /* Packet fragment received */
                        len = undi_isr.FrameLength;
                        frag_len = undi_isr.BufferLength;
+                       reserve_len = ( -undi_isr.FrameHeaderLength &
+                                       ( UNDI_RX_ALIGN - 1 ) );
                        if ( ( len == 0 ) || ( len < frag_len ) ) {
                                /* Don't laugh.  VMWare does it. */
                                DBGC ( undinic, "UNDINIC %p reported insane "
@@ -354,15 +360,17 @@ static void undinet_poll ( struct net_device *netdev ) {
                                netdev_rx_err ( netdev, NULL, -EINVAL );
                                break;
                        }
-                       if ( ! iobuf )
-                               iobuf = alloc_iob ( len );
                        if ( ! iobuf ) {
-                               DBGC ( undinic, "UNDINIC %p could not "
-                                      "allocate %zd bytes for RX buffer\n",
-                                      undinic, len );
-                               /* Fragment will be dropped */
-                               netdev_rx_err ( netdev, NULL, -ENOMEM );
-                               goto done;
+                               iobuf = alloc_iob ( reserve_len + len );
+                               if ( ! iobuf ) {
+                                       DBGC ( undinic, "UNDINIC %p could not "
+                                              "allocate %zd bytes for RX "
+                                              "buffer\n", undinic, len );
+                                       /* Fragment will be dropped */
+                                       netdev_rx_err ( netdev, NULL, -ENOMEM );
+                                       goto done;
+                               }
+                               iob_reserve ( iobuf, reserve_len );
                        }
                        max_frag_len = iob_tailroom ( iobuf );
                        if ( frag_len > max_frag_len ) {