hw/net/allwinner-sun8i-emac: Correctly byteswap descriptor fields

In allwinner-sun8i-emac we just read directly from guest memory into
a host FrameDescriptor struct and back.  This only works on
little-endian hosts.  Reading and writing of descriptors is already
abstracted into functions; make those functions also handle the
byte-swapping so that TransferDescriptor structs as seen by the rest
of the code are always in host-order, and fix two places that were
doing ad-hoc descriptor reading without using the functions.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230424165053.1428857-3-peter.maydell@linaro.org
(cherry picked from commit a4ae17e5ec512862bf73e40dfbb1e7db71f2c1e7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/net/allwinner-sun8i-emac.c

@@ -350,8 +350,13 @@ static void allwinner_sun8i_emac_get_desc(AwSun8iEmacState *s,
                                           FrameDescriptor *desc,
                                           uint32_t phys_addr)
 {
-    dma_memory_read(&s->dma_as, phys_addr, desc, sizeof(*desc),
+    uint32_t desc_words[4];
+    dma_memory_read(&s->dma_as, phys_addr, &desc_words, sizeof(desc_words),
                     MEMTXATTRS_UNSPECIFIED);
+    desc->status = le32_to_cpu(desc_words[0]);
+    desc->status2 = le32_to_cpu(desc_words[1]);
+    desc->addr = le32_to_cpu(desc_words[2]);
+    desc->next = le32_to_cpu(desc_words[3]);
 }
 
 static uint32_t allwinner_sun8i_emac_next_desc(AwSun8iEmacState *s,
@@ -400,10 +405,15 @@ static uint32_t allwinner_sun8i_emac_tx_desc(AwSun8iEmacState *s,
 }
 
 static void allwinner_sun8i_emac_flush_desc(AwSun8iEmacState *s,
-                                            FrameDescriptor *desc,
+                                            const FrameDescriptor *desc,
                                             uint32_t phys_addr)
 {
-    dma_memory_write(&s->dma_as, phys_addr, desc, sizeof(*desc),
+    uint32_t desc_words[4];
+    desc_words[0] = cpu_to_le32(desc->status);
+    desc_words[1] = cpu_to_le32(desc->status2);
+    desc_words[2] = cpu_to_le32(desc->addr);
+    desc_words[3] = cpu_to_le32(desc->next);
+    dma_memory_write(&s->dma_as, phys_addr, &desc_words, sizeof(desc_words),
                      MEMTXATTRS_UNSPECIFIED);
 }
 
@@ -638,8 +648,7 @@ static uint64_t allwinner_sun8i_emac_read(void *opaque, hwaddr offset,
         break;
     case REG_TX_CUR_BUF:        /* Transmit Current Buffer */
         if (s->tx_desc_curr != 0) {
-            dma_memory_read(&s->dma_as, s->tx_desc_curr, &desc, sizeof(desc),
-                            MEMTXATTRS_UNSPECIFIED);
+            allwinner_sun8i_emac_get_desc(s, &desc, s->tx_desc_curr);
             value = desc.addr;
         } else {
             value = 0;
@@ -652,8 +661,7 @@ static uint64_t allwinner_sun8i_emac_read(void *opaque, hwaddr offset,
         break;
     case REG_RX_CUR_BUF:        /* Receive Current Buffer */
         if (s->rx_desc_curr != 0) {
-            dma_memory_read(&s->dma_as, s->rx_desc_curr, &desc, sizeof(desc),
-                            MEMTXATTRS_UNSPECIFIED);
+            allwinner_sun8i_emac_get_desc(s, &desc, s->rx_desc_curr);
             value = desc.addr;
         } else {
             value = 0;