netdev - Re: [net-next,02/13] tg3: Cleanup transmit error path

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Date:	Thu, 2 Jun 2011 16:01:39 -0700
From:	"Matt Carlson" <mcarlson@...adcom.com>
To:	"Alex Williamson" <alex.williamson@...hat.com>
cc:	"Matthew Carlson" <mcarlson@...adcom.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [net-next,02/13] tg3: Cleanup transmit error path

On Thu, Jun 02, 2011 at 03:18:35PM -0700, Alex Williamson wrote:
> On Thu, 2011-05-19 at 12:12 +0000, Matt Carlson wrote:
> > This patch consolidates the skb cleanup code into a function named
> > tg3_skb_error_unmap().  The modification addresses a long-standing bug
> > where pci_unmap_single() was incorrectly being called instead of
> > pci_unmap_page() in tigon3_dma_hwbug_workaround().
> 
> This patch doesn't behave well when an iommu (VT-d) is involved.
> Booting an X58 chipset based system with intel_iommu=on with 3.0.0-rc1
> results in the warning below.  Looks like the driver is trying to unmap
> 0x0.  Eventually something worse happens and the system reports a few
> iommu faults from the device before panicing.  Neither problem is
> observed if 432aa7ed is reverted.  tg3 device in use is a BCM5755.
> Thanks,
> 
> Alex
> 
> WARNING: at drivers/pci/intel-iommu.c:2888 intel_unmap_page+0x15c/0x180()
> Hardware name: 4157CTO
> Driver unmaps unmatched page at PFN 0
> Modules linked in: nfs lockd auth_rpcgss nfs_acl ipt_MASQUERADE iptable_nat nf_nat iptable_mangle tun autofs4 sunrpc cpufreq_ondemand acpi_cpufreq freq_table mperf bridge stp llc ipv6 dm_mirror dm_region_hash dm_log kvm_intel kvm sg microcode serio_raw wmi i2c_i801 i2c_core iTCO_wdt iTCO_vendor_support tg3 ext4 mbcache jbd2 raid1 raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx sr_mod cdrom sd_mod crc_t10dif floppy dm_mod [last unloaded: scsi_wait_scan]
> Pid: 2604, comm: libvirtd Not tainted 3.0.0-rc1+ #184
> Call Trace:
>  [<ffffffff8105c7df>] warn_slowpath_common+0x7f/0xc0
>  [<ffffffff8105c8d6>] warn_slowpath_fmt+0x46/0x50
>  [<ffffffff81245b8b>] ? find_iova+0x5b/0xa0
>  [<ffffffff8124a60c>] intel_unmap_page+0x15c/0x180
>  [<ffffffffa0128d48>] tg3_skb_error_unmap+0xb8/0x130 [tg3]
>  [<ffffffffa0136041>] tg3_start_xmit+0x661/0xde0 [tg3]
>  [<ffffffffa01363dd>] ? tg3_start_xmit+0x9fd/0xde0 [tg3]
>  [<ffffffff8138d7fe>] dev_hard_start_xmit+0x31e/0x6c0
>  [<ffffffff813a9f5f>] sch_direct_xmit+0xef/0x1c0
>  [<ffffffff8138dd38>] dev_queue_xmit+0x198/0x5f0
>  [<ffffffffa028d2ac>] br_dev_queue_push_xmit+0x6c/0xa0 [bridge]
>  [<ffffffffa028d478>] br_forward_finish+0x58/0x60 [bridge]
>  [<ffffffffa028d4f8>] __br_deliver+0x78/0xf0 [bridge]
>  [<ffffffff814367a9>] ? packet_rcv+0x59/0x450
>  [<ffffffffa028d5a5>] br_deliver+0x35/0x40 [bridge]
>  [<ffffffffa028b8c4>] br_dev_xmit+0x114/0x180 [bridge]
>  [<ffffffff8138d7fe>] dev_hard_start_xmit+0x31e/0x6c0
>  [<ffffffff8138df95>] dev_queue_xmit+0x3f5/0x5f0
>  [<ffffffff813d0c2e>] ip_finish_output+0x16e/0x340
>  [<ffffffff813d1110>] ip_output+0xb0/0xc0
>  [<ffffffff813cfdc3>] ? __ip_local_out+0xa3/0xb0
>  [<ffffffff813d0129>] ip_local_out+0x29/0x30
>  [<ffffffff813d0604>] ip_queue_xmit+0x164/0x410
>  [<ffffffff813e5e5c>] tcp_transmit_skb+0x41c/0x910
>  [<ffffffff813e86f7>] tcp_write_xmit+0x1e7/0x9d0
>  [<ffffffff813e8f46>] __tcp_push_pending_frames+0x26/0xc0
>  [<ffffffff813d77be>] tcp_push+0x6e/0x90
>  [<ffffffff813db4f9>] tcp_sendmsg+0x759/0xc00
>  [<ffffffff813fdaa8>] inet_sendmsg+0x48/0xb0
>  [<ffffffff811cd7f3>] ? selinux_socket_sendmsg+0x23/0x30
>  [<ffffffff81377e52>] sock_sendmsg+0xe2/0x120
>  [<ffffffff8100a7e4>] ? __switch_to+0x194/0x320
>  [<ffffffff81377ed1>] kernel_sendmsg+0x41/0x60

Does this patch fix the problem?

Subject: [PATCH] tg3: Fix tg3_skb_error_unmap()

This function attempts to free one fragment beyond the number of
fragments that were actually mapped.  This patch brings back the limit
to the correct spot.

Signed-off-by: Matt Carlson <mcarlson@...adcom.com>
---
 drivers/net/tg3.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 8ece39b..3d239ab 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -5771,7 +5771,7 @@ static void tg3_skb_error_unmap(struct tg3_napi *tnapi,
 			 dma_unmap_addr(txb, mapping),
 			 skb_headlen(skb),
 			 PCI_DMA_TODEVICE);
-	for (i = 0; i <= last; i++) {
+	for (i = 0; i < last; i++) {
 		skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 
 		entry = NEXT_TX(entry);
-- 
1.7.3.4


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