[Qemu-devel] [PATCH 1/2] e1000: defer packets until BM enabled

[Amos Kong <akong@redhat.com>]

From: "Michael S. Tsirkin" <mst@redhat.com>

Some guests seem to set BM for e1000 after enabling RX.
If packets arrive in the window, device is wedged.
Probably works by luck on real hardware, work around
this by making can_receive depend on BM. This patch
defer transmit packets, only start transmit when BM
is enabled.

Tested-by: Gabriel Somlo <somlo@cmu.edu>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Amos Kong <akong@redhat.com>
---
 hw/net/e1000.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index e33a4da..ec9224b 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -33,6 +33,7 @@
 #include "sysemu/sysemu.h"
 #include "sysemu/dma.h"
 #include "qemu/iov.h"
+#include "qemu/range.h"
 
 #include "e1000_regs.h"
 
@@ -790,6 +791,11 @@ start_xmit(E1000State *s)
     struct e1000_tx_desc desc;
     uint32_t tdh_start = s->mac_reg[TDH], cause = E1000_ICS_TXQE;
 
+    if (!(d->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
+        DBGOUT(TX, "BM disabled\n");
+        return;
+    }
+
     if (!(s->mac_reg[TCTL] & E1000_TCTL_EN)) {
         DBGOUT(TX, "tx disabled\n");
         return;
@@ -923,7 +929,9 @@ e1000_can_receive(NetClientState *nc)
     E1000State *s = qemu_get_nic_opaque(nc);
 
     return (s->mac_reg[STATUS] & E1000_STATUS_LU) &&
-        (s->mac_reg[RCTL] & E1000_RCTL_EN) && e1000_has_rxbufs(s, 1);
+        (s->mac_reg[RCTL] & E1000_RCTL_EN) &&
+        (s->parent_obj.config[PCI_COMMAND] & PCI_COMMAND_MASTER) &&
+        e1000_has_rxbufs(s, 1);
 }
 
 static uint64_t rx_desc_base(E1000State *s)
@@ -1529,6 +1537,21 @@ static NetClientInfo net_e1000_info = {
     .link_status_changed = e1000_set_link_status,
 };
 
+static void e1000_write_config(PCIDevice *pci_dev, uint32_t address,
+                                uint32_t val, int len)
+{
+    E1000State *s = E1000(pci_dev);
+
+    pci_default_write_config(pci_dev, address, val, len);
+
+    if (range_covers_byte(address, len, PCI_COMMAND) &&
+        (pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
+        qemu_flush_queued_packets(qemu_get_queue(s->nic));
+        start_xmit(s);
+    }
+}
+
+
 static int pci_e1000_init(PCIDevice *pci_dev)
 {
     DeviceState *dev = DEVICE(pci_dev);
@@ -1539,6 +1562,8 @@ static int pci_e1000_init(PCIDevice *pci_dev)
     int i;
     uint8_t *macaddr;
 
+    pci_dev->config_write = e1000_write_config;
+
     pci_conf = pci_dev->config;
 
     /* TODO: RST# value should be 0, PCI spec 6.2.4 */
-- 
2.1.0