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From: Leonid Bloch <leonid.bloch@ravellosystems.com>
Date: Mon,  9 Nov 2015 16:59:28 +0200
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Subject: [Qemu-devel] [PATCH v5 6/8] e1000: Fixing the received/transmitted
	octets' counters
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To: qemu-devel@nongnu.org
Cc: Dmitry Fleytman <dmitry@daynix.com>, Jason Wang <jasowang@redhat.com>, Leonid Bloch <leonid@daynix.com>, Shmulik Ladkani <shmulik.ladkani@ravellosystems.com>

Previously, these 64-bit registers did not stick at their maximal
values when (and if) they reached them, as they should do, according to
the specs.

This patch introduces a function that takes care of such registers,
avoiding code duplication, making the relevant parts more compatible
with the QEMU coding style, while ensuring that in the unlikely case
of reaching the maximal value, the counter will stick there, as it
supposed to.

Signed-off-by: Leonid Bloch <leonid.bloch@ravellosystems.com>
Signed-off-by: Dmitry Fleytman <dmitry.fleytman@ravellosystems.com>
---
 hw/net/e1000.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index c301637..c262663 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -588,6 +588,20 @@ inc_reg_if_not_full(E1000State *s, int index)
     }
 }
 
+static void
+grow_8reg_if_not_full(E1000State *s, int index, int size)
+{
+    uint64_t sum = s->mac_reg[index] | (uint64_t)s->mac_reg[index+1] << 32;
+
+    if (sum + size < sum) {
+        sum = ~0ULL;
+    } else {
+        sum += size;
+    }
+    s->mac_reg[index] = sum;
+    s->mac_reg[index+1] = sum >> 32;
+}
+
 static inline int
 vlan_enabled(E1000State *s)
 {
@@ -637,7 +651,7 @@ static void
 xmit_seg(E1000State *s)
 {
     uint16_t len, *sp;
-    unsigned int frames = s->tx.tso_frames, css, sofar, n;
+    unsigned int frames = s->tx.tso_frames, css, sofar;
     struct e1000_tx *tp = &s->tx;
 
     if (tp->tse && tp->cptse) {
@@ -686,10 +700,8 @@ xmit_seg(E1000State *s)
     }
 
     inc_reg_if_not_full(s, TPT);
+    grow_8reg_if_not_full(s, TOTL, s->tx.size);
     s->mac_reg[GPTC] = s->mac_reg[TPT];
-    n = s->mac_reg[TOTL];
-    if ((s->mac_reg[TOTL] += s->tx.size) < n)
-        s->mac_reg[TOTH]++;
 }
 
 static void
@@ -1104,11 +1116,9 @@ e1000_receive_iov(NetClientState *nc, const struct iovec *iov, int iovcnt)
     /* TOR - Total Octets Received:
      * This register includes bytes received in a packet from the <Destination
      * Address> field through the <CRC> field, inclusively.
+     * Always include FCS length (4) in size.
      */
-    n = s->mac_reg[TORL] + size + /* Always include FCS length. */ 4;
-    if (n < s->mac_reg[TORL])
-        s->mac_reg[TORH]++;
-    s->mac_reg[TORL] = n;
+    grow_8reg_if_not_full(s, TORL, size+4);
 
     n = E1000_ICS_RXT0;
     if ((rdt = s->mac_reg[RDT]) < s->mac_reg[RDH])
-- 
2.4.3