[Qemu-devel] [PATCH] e1000: use MII status register for link up/down

[Bjørn Mork]

Some guests will use the standard MII status register
to verify link state.  They will not notice link changes
unless this register is updated.

Verified with Linux 3.0 and Windows XP guests.

Without this patch, ethtool will report speed and duplex as
unknown when the link is down, but still report the link as
up.  This is because the Linux e1000 driver checks the
mac_reg[STATUS] register link state before it checks speed
and duplex, but uses the phy_reg[PHY_STATUS] register for
the actual link state check.  Fix by updating both registers
on link state changes.

Linux guest before:

 (qemu) set_link e1000.0 off

 kvm-sid:~# ethtool eth0
 Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: Unknown
        Supports Wake-on: umbg
        Wake-on: d
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

 (qemu) set_link e1000.0 on

Linux guest after:

 (qemu) set_link e1000.0 off
 [   63.384221] e1000: eth0 NIC Link is Down

 kvm-sid:~# ethtool eth0
 Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: Unknown
        Supports Wake-on: umbg
        Wake-on: d
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: no

 (qemu) set_link e1000.0 on
 [   84.304582] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: 
RX

Signed-off-by: Bjørn Mork <address@hidden>
---
 hw/e1000.c    |    7 +++++--
 hw/e1000_hw.h |   17 +++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/hw/e1000.c b/hw/e1000.c
index 29b453f..a6d12c5 100644
--- a/hw/e1000.c
+++ b/hw/e1000.c
@@ -617,10 +617,13 @@ e1000_set_link_status(VLANClientState *nc)
     E1000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
     uint32_t old_status = s->mac_reg[STATUS];
 
-    if (nc->link_down)
+    if (nc->link_down) {
         s->mac_reg[STATUS] &= ~E1000_STATUS_LU;
-    else
+        s->phy_reg[PHY_STATUS] &= ~MII_SR_LINK_STATUS;
+    } else {
         s->mac_reg[STATUS] |= E1000_STATUS_LU;
+        s->phy_reg[PHY_STATUS] |= MII_SR_LINK_STATUS;
+    }
 
     if (s->mac_reg[STATUS] != old_status)
         set_ics(s, 0, E1000_ICR_LSC);
diff --git a/hw/e1000_hw.h b/hw/e1000_hw.h
index 9bd8a4b..2e341ac 100644
--- a/hw/e1000_hw.h
+++ b/hw/e1000_hw.h
@@ -349,6 +349,23 @@
 #define M88E1000_PHY_VCO_REG_BIT8  0x100 /* Bits 8 & 11 are adjusted for */
 #define M88E1000_PHY_VCO_REG_BIT11 0x800    /* improved BER performance */
 
+/* PHY Status Register */
+#define MII_SR_EXTENDED_CAPS     0x0001        /* Extended register 
capabilities */
+#define MII_SR_JABBER_DETECT     0x0002        /* Jabber Detected */
+#define MII_SR_LINK_STATUS       0x0004        /* Link Status 1 = link */
+#define MII_SR_AUTONEG_CAPS      0x0008        /* Auto Neg Capable */
+#define MII_SR_REMOTE_FAULT      0x0010        /* Remote Fault Detect */
+#define MII_SR_AUTONEG_COMPLETE  0x0020        /* Auto Neg Complete */
+#define MII_SR_PREAMBLE_SUPPRESS 0x0040        /* Preamble may be suppressed */
+#define MII_SR_EXTENDED_STATUS   0x0100        /* Ext. status info in Reg 0x0F 
*/
+#define MII_SR_100T2_HD_CAPS     0x0200        /* 100T2 Half Duplex Capable */
+#define MII_SR_100T2_FD_CAPS     0x0400        /* 100T2 Full Duplex Capable */
+#define MII_SR_10T_HD_CAPS       0x0800        /* 10T   Half Duplex Capable */
+#define MII_SR_10T_FD_CAPS       0x1000        /* 10T   Full Duplex Capable */
+#define MII_SR_100X_HD_CAPS      0x2000        /* 100X  Half Duplex Capable */
+#define MII_SR_100X_FD_CAPS      0x4000        /* 100X  Full Duplex Capable */
+#define MII_SR_100T4_CAPS        0x8000        /* 100T4 Capable */
+
 /* Interrupt Cause Read */
 #define E1000_ICR_TXDW          0x00000001 /* Transmit desc written back */
 #define E1000_ICR_TXQE          0x00000002 /* Transmit Queue empty */
-- 
1.7.2.5