[PATCH 2/2] e1000e: make TX reentrant

[Jason Wang <jasowang@redhat.com>]

In loopback mode, e1000e RX can DMA into TX doorbell which requires
TX to be reentrant. This patch make e1000e's TX routine reentrant by
introducing a per device boolean for recording whether or not a TX
rountine is being called and return early.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/net/e1000e_core.c | 8 ++++++++
 hw/net/e1000e_core.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
index bcd186cac5..8126a644a5 100644
--- a/hw/net/e1000e_core.c
+++ b/hw/net/e1000e_core.c
@@ -923,6 +923,12 @@ e1000e_start_xmit(E1000ECore *core, const E1000E_TxRing *txr)
         return;
     }
 
+    if (core->sending) {
+        return;
+    }
+
+    core->sending = true;
+
     while (!e1000e_ring_empty(core, txi)) {
         base = e1000e_ring_head_descr(core, txi);
 
@@ -940,6 +946,8 @@ e1000e_start_xmit(E1000ECore *core, const E1000E_TxRing *txr)
     if (!ide || !e1000e_intrmgr_delay_tx_causes(core, &cause)) {
         e1000e_set_interrupt_cause(core, cause);
     }
+
+    core->sending = false;
 }
 
 static bool
diff --git a/hw/net/e1000e_core.h b/hw/net/e1000e_core.h
index aee32f7e48..4679c1761f 100644
--- a/hw/net/e1000e_core.h
+++ b/hw/net/e1000e_core.h
@@ -114,6 +114,7 @@ struct E1000Core {
     void (*owner_start_recv)(PCIDevice *d);
 
     uint32_t msi_causes_pending;
+    bool sending;
 };
 
 void
-- 
2.20.1