Reduce spurious packet drops on RX ring empty when in c+ mode by verifying that
we have at least 1 buffer ahead of the time.
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
hw/rtl8139.c | 43 +++++++++++++++++++++++++++++--------------
1 files changed, 29 insertions(+), 14 deletions(-)
diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index 3753950..c654d5d 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -84,6 +84,19 @@
#define VLAN_TCI_LEN 2
#define VLAN_HLEN (ETHER_TYPE_LEN + VLAN_TCI_LEN)
+/* w0 ownership flag */
+#define CP_RX_OWN (1<<31)
+/* w0 end of ring flag */
+#define CP_RX_EOR (1<<30)
+/* w0 bits 0...12 : buffer size */
+#define CP_RX_BUFFER_SIZE_MASK ((1<<13) - 1)
+/* w1 tag available flag */
+#define CP_RX_TAVA (1<<16)
+/* w1 bits 0...15 : VLAN tag */
+#define CP_RX_VLAN_TAG_MASK ((1<<16) - 1)
+/* w2 low 32bit of Rx buffer ptr */
+/* w3 high 32bit of Rx buffer ptr */
+
#if defined (DEBUG_RTL8139)
# define DPRINTF(fmt, ...) \
do { fprintf(stderr, "RTL8139: " fmt, ## __VA_ARGS__); } while (0)
@@ -805,6 +818,21 @@ static inline target_phys_addr_t rtl8139_addr64(uint32_t
low, uint32_t high)
#endif
}
+/* Verify that we have at least one available rx buffer */
+static int rtl8139_cp_has_rxbuf(RTL8139State *s)
+{
+ uint32_t val, rxdw0;
+ target_phys_addr_t cplus_rx_ring_desc = rtl8139_addr64(s->RxRingAddrLO,
+ s->RxRingAddrHI);
+ cplus_rx_ring_desc += 16 * s->currCPlusRxDesc;
+ cpu_physical_memory_read(cplus_rx_ring_desc, (uint8_t *)&val, 4);
+ rxdw0 = le32_to_cpu(val);
+ if (rxdw0 & CP_RX_OWN)
+ return 1;
+ else
+ return 0;
+}
+
static int rtl8139_can_receive(VLANClientState *nc)
{
RTL8139State *s = DO_UPCAST(NICState, nc, nc)->opaque;
@@ -819,7 +847,7 @@ static int rtl8139_can_receive(VLANClientState *nc)
if (rtl8139_cp_receiver_enabled(s)) {
/* ??? Flow control not implemented in c+ mode.
This is a hack to work around slirp deficiencies anyway. */
- return 1;
+ return rtl8139_cp_has_rxbuf(s);
} else {
avail = MOD2(s->RxBufferSize + s->RxBufPtr - s->RxBufAddr,
s->RxBufferSize);
@@ -965,19 +993,6 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc,
const uint8_t *buf, size_
/* begin C+ receiver mode */
-/* w0 ownership flag */
-#define CP_RX_OWN (1<<31)
-/* w0 end of ring flag */
-#define CP_RX_EOR (1<<30)
-/* w0 bits 0...12 : buffer size */
-#define CP_RX_BUFFER_SIZE_MASK ((1<<13) - 1)
-/* w1 tag available flag */
-#define CP_RX_TAVA (1<<16)
-/* w1 bits 0...15 : VLAN tag */
-#define CP_RX_VLAN_TAG_MASK ((1<<16) - 1)
-/* w2 low 32bit of Rx buffer ptr */
-/* w3 high 32bit of Rx buffer ptr */
-
int descriptor = s->currCPlusRxDesc;
target_phys_addr_t cplus_rx_ring_desc;
