From 5fcf8fae232fc3c0842a3777e6561e50c77b65ec Mon Sep 17 00:00:00 2001
From: aliguori <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162>
Date: Fri, 20 Mar 2009 16:13:47 +0000
Subject: [PATCH 3/6] e1000: Fix RX descriptor low threshold interrupt logic (Alex Williamson)

The RXDMT0 interrupt is supposed to fire when the number of free
RX descriptors drops to some fraction of the total descriptors.
However in practice, it seems like we're adding this interrupt
cause on every RX.  Fix the logic to treat (tail - head) as the
number of free entries rather than the number of used entries.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Upstream-status: applied(qemu/trunk)
Bugzilla: 491930
Acked-by: Dor Laor <dlaor@redhat.com>
Acked-by: john cooper <john.cooper@redhat.com>
Acked-by: Juan Quintela <quintela@redhat.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6864 c046a42c-6fe2-441c-8c8c-71466251a162
---
 qemu/hw/e1000.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/qemu/hw/e1000.c b/qemu/hw/e1000.c
index eaed351..f6f0135 100644
--- a/qemu/hw/e1000.c
+++ b/qemu/hw/e1000.c
@@ -667,8 +667,8 @@ e1000_receive(void *opaque, const uint8_t *buf, int size)
     n = E1000_ICS_RXT0;
     if ((rdt = s->mac_reg[RDT]) < s->mac_reg[RDH])
         rdt += s->mac_reg[RDLEN] / sizeof(desc);
-    if (((rdt - s->mac_reg[RDH]) * sizeof(desc)) << s->rxbuf_min_shift >=
-        s->mac_reg[RDLEN])
+    if (((rdt - s->mac_reg[RDH]) * sizeof(desc)) <= s->mac_reg[RDLEN] >>
+        s->rxbuf_min_shift)
         n |= E1000_ICS_RXDMT0;
 
     set_ics(s, 0, n);
-- 
1.6.1