[PATCH] intel-iommu: don't call domain_exit if can not attach with iommu

[Yinghai Lu <yinghai@kernel.org>]

found when a lot of ixgbevf are used with intel iommu, will get crash

> 
> eth304 ip=192.171.178.102 mac=56:95:16:88:4C:C1 pci=0000:0e:18.3 drv=ixgbevf
> eth305 ip=192.171.179.102 mac=D6:41:8C:4A:87:B3 pci=0000:0e:18.5 drv=ixgbevf
> [ 9534.886519] BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000008
> [ 9534.889775] Call Trace:
> [ 9534.889775]  [<ffffffff81406a3d>] domain_remove_dev_info+0x34/0xcf
> [ 9534.889775]  [<ffffffff81408a1d>] domain_exit+0x23/0xc4
> [ 9534.889775]  [<ffffffff81409c1c>] T.953+0x173/0x342
> [ 9534.889775]  [<ffffffff81409fd0>] __intel_map_single+0x63/0x1b3
> [ 9534.889775]  [<ffffffff8140a22a>] intel_alloc_coherent+0xc7/0xee
> [ 9534.889775]  [<ffffffff816c3e7d>] ? ixgbevf_setup_tx_resources+0x2f/0x12c
> [ 9534.889775]  [<ffffffff816c3f36>] ixgbevf_setup_tx_resources+0xe8/0x12c
> [ 9534.889775]  [<ffffffff816c42d2>] ixgbevf_open+0x7a/0x160
> [ 9534.889775]  [<ffffffff81adf21e>] __dev_open+0x8e/0xbc
> [ 9534.889775]  [<ffffffff81adb716>] __dev_change_flags+0xad/0x130
> [ 9534.889775]  [<ffffffff81adf15a>] dev_change_flags+0x21/0x57
> [ 9534.889775]  [<ffffffff81b211e5>] devinet_ioctl+0x29d/0x541
> [ 9534.889775]  [<ffffffff810a4b92>] ? trace_hardirqs_off_caller+0x1f/0xa9
> [ 9534.889775]  [<ffffffff81b22801>] inet_ioctl+0x8f/0xa7
> [ 9534.889775]  [<ffffffff81acc258>] sock_do_ioctl+0x29/0x48
> [ 9534.889775]  [<ffffffff81acca64>] sock_ioctl+0x1fe/0x20d
> [ 9534.889775]  [<ffffffff8113b86a>] vfs_ioctl+0x32/0xa6
> [ 9534.889775]  [<ffffffff8113bd04>] do_vfs_ioctl+0x2b0/0x2cb
> [ 9534.889775]  [<ffffffff81033c4c>] ? sysret_check+0x27/0x62
> [ 9534.889775]  [<ffffffff8113bd66>] sys_ioctl+0x47/0x6a
> [ 9534.889775]  [<ffffffff81033c1b>] system_call_fastpath+0x16/0x1b
> [ 9534.889775] Code: cd 7f cc ff 41 54 9d 48 83 c4 20 5b 41 5c 41 5d 41
> 5e c9 c3 55 48 89 e5 e8 11 ff ff ff c9 c3 55 48 89 e5 53 48 89 fb 48 83
> ec 08 <48> 8b 47 08 4c 8b 00 49 39 f8 74 1d 48 89 f9 48 c7 c2 7f e9 18
> [ 9534.889775] RIP  [<ffffffff813ddf94>] list_del+0xc/0x8b
> [ 9534.889775]  RSP <ffff88c070373af8>
> [ 9534.889775] CR2: 0000000000000008
> [ 9534.889775] ---[ end trace 072bd8cdb08a760c ]---
> xifconfig8_2x_vf.sh: line 10: 28555 Killed                  ifconfig
> $DEV $IP
> 

when intel_iommu=off or iommu=pt is used, will work well.

root cause:
domain is initialized after trying attached it,

if it can not be attached, don't call domain_exit yet. it will cause kernel crash in domain_exit()

after patch will will get error instead of crash.

[ 1781.910241] IOMMU: no free domain ids
[ 1781.910244] Allocating domain for 0000:d0:1f.5 failed
SIOCSIFFLAGS: Cannot allocate memory


Signed-off-by: Yinghai Lu <yinghai@kernel.org>

Index: linux-2.6/drivers/pci/intel-iommu.c
===================================================================
--- linux-2.6.orig/drivers/pci/intel-iommu.c
+++ linux-2.6/drivers/pci/intel-iommu.c
@@ -1853,7 +1857,7 @@ static struct dmar_domain *get_domain_fo
 
 	ret = iommu_attach_domain(domain, iommu);
 	if (ret) {
-		domain_exit(domain);
+		free_domain_mem(domain);
 		goto error;
 	}