From: Andy Gospodarek <gospo@redhat.com>
Date: Thu, 25 Feb 2010 16:44:45 -0500
Subject: [net] e1000e: disable NFS filtering capabilites in ICH hw
Message-id: <20100225164445.GB24578@gospo.rdu.redhat.com>
Patchwork-id: 23436
O-Subject: [PATCH RHEL5.5] e1000e: disable NFS filtering capabilites in ICH
	hardware
Bugzilla: 558809
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>
RH-Acked-by: Jiri Pirko <jpirko@redhat.com>
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: David S. Miller <davem@redhat.com>
RH-Acked-by: Steve Dickson <SteveD@redhat.com>

For quite a while we have been tracking down a problem found when
running the connectathon test on some Intel reference designs.  We were
able to narrow this down to a specific set of commands when running the
NFSv2 portion of the test that would result in skb_shared_info
corruption that was pointed out when running the -debug variant of the
kernel.

It turns out that ICH-based e1000e hardware has some NFS filtering
capability that doesn't quite work as expected.  After I looked at the
Programmer's Guide from Intel, it was clear we could disable this
feature.  Since disabling it we are not seeing any skb_shared_info
corruption.

This patch has not been posted upstream, but I am working with Intel to
have this done shortly.

The fix has been verified by Neil Horman and Intel.

This will resolve RHBZ 558809.


diff --git a/drivers/net/e1000e/defines.h b/drivers/net/e1000e/defines.h
index 1190167..a468447 100644
--- a/drivers/net/e1000e/defines.h
+++ b/drivers/net/e1000e/defines.h
@@ -320,6 +320,8 @@
 #define E1000_RXCSUM_IPPCSE    0x00001000   /* IP payload checksum enable */
 
 /* Header split receive */
+#define E1000_RFCTL_NFSW_DIS            0x00000040
+#define E1000_RFCTL_NFSR_DIS            0x00000080
 #define E1000_RFCTL_ACK_DIS             0x00001000
 #define E1000_RFCTL_EXTEN               0x00008000
 #define E1000_RFCTL_IPV6_EX_DIS         0x00010000
diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
index f911baa..e7b2eb3 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -2441,6 +2441,18 @@ static void e1000_setup_rctl(struct e1000_adapter *adapter)
 		ew32(PSRCTL, psrctl);
 	}
 
+	/*
+	 * Disable hardware filtering/packet split for NFS write request
+	 * headers and NFS read reply headers on ICH platforms due to
+	 * possible skb_shared_info corruption with some MTUs.
+	 */
+	if (adapter->flags & FLAG_IS_ICH) {
+		rfctl = er32(RFCTL);
+		rfctl |= (E1000_RFCTL_NFSW_DIS |
+			  E1000_RFCTL_NFSR_DIS);
+		ew32(RFCTL, rfctl);
+	}
+
 	ew32(RCTL, rctl);
 	/* just started the receive unit, no need to restart */
 	adapter->flags &= ~FLAG_RX_RESTART_NOW;