[PATCH v3 ] iommu/vt-d: Fix panic after kexec -p for kdump

John Donnelly
2019-10-22T02:48:18Z

This cures a panic on restart after a kexec operation on 5.3 and 5.4
kernels.

The underlying state of the iommu registers (iommu->flags &
VTD_FLAG_TRANS_PRE_ENABLED) on a restart results in a domain being marked as
"DEFER_DEVICE_DOMAIN_INFO" that produces an Oops in identity_mapping().

[ 43.654737] BUG: kernel NULL pointer dereference, address:
0000000000000056
[ 43.655720] #PF: supervisor read access in kernel mode
[ 43.655720] #PF: error_code(0x0000) - not-present page
[ 43.655720] PGD 0 P4D 0
[ 43.655720] Oops: 0000 [#1] SMP PTI
[ 43.655720] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
5.3.2-1940.el8uek.x86_64 #1
[ 43.655720] Hardware name: Oracle Corporation ORACLE SERVER
X5-2/ASM,MOTHERBOARD,1U, BIOS 30140300 09/20/2018
[ 43.655720] RIP: 0010:iommu_need_mapping+0x29/0xd0
[ 43.655720] Code: 00 0f 1f 44 00 00 48 8b 97 70 02 00 00 48 83 fa ff
74 53 48 8d 4a ff b8 01 00 00 00 48 83 f9 fd 76 01 c3 48 8b 35 7f 58 e0
01 <48> 39 72 58 75 f2 55 48 89 e5 41 54 53 48 8b 87 28 02 00 00 4c 8b
[ 43.655720] RSP: 0018:ffffc9000001b9b0 EFLAGS: 00010246
[ 43.655720] RAX: 0000000000000001 RBX: 0000000000001000 RCX:
fffffffffffffffd
[ 43.655720] RDX: fffffffffffffffe RSI: ffff8880719b8000 RDI:
ffff8880477460b0
[ 43.655720] RBP: ffffc9000001b9e8 R08: 0000000000000000 R09:
ffff888047c01700
[ 43.655720] R10: 00002194036fc692 R11: 0000000000000000 R12:
0000000000000000
[ 43.655720] R13: ffff8880477460b0 R14: 0000000000000cc0 R15:
ffff888072d2b558
[ 43.655720] FS: 0000000000000000(0000) GS:ffff888071c00000(0000)
knlGS:0000000000000000
[ 43.655720] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 43.655720] CR2: 0000000000000056 CR3: 000000007440a002 CR4:
00000000001606b0
[ 43.655720] Call Trace:
[ 43.655720] ? intel_alloc_coherent+0x2a/0x180
[ 43.655720] ? __schedule+0x2c2/0x650
[ 43.655720] dma_alloc_attrs+0x8c/0xd0
[ 43.655720] dma_pool_alloc+0xdf/0x200
[ 43.655720] ehci_qh_alloc+0x58/0x130
[ 43.655720] ehci_setup+0x287/0x7ba
[ 43.655720] ? _dev_info+0x6c/0x83
[ 43.655720] ehci_pci_setup+0x91/0x436
[ 43.655720] usb_add_hcd.cold.48+0x1d4/0x754
[ 43.655720] usb_hcd_pci_probe+0x2bc/0x3f0
[ 43.655720] ehci_pci_probe+0x39/0x40
[ 43.655720] local_pci_probe+0x47/0x80
[ 43.655720] pci_device_probe+0xff/0x1b0
[ 43.655720] really_probe+0xf5/0x3a0
[ 43.655720] driver_probe_device+0xbb/0x100
[ 43.655720] device_driver_attach+0x58/0x60
[ 43.655720] __driver_attach+0x8f/0x150
[ 43.655720] ? device_driver_attach+0x60/0x60
[ 43.655720] bus_for_each_dev+0x74/0xb0
[ 43.655720] driver_attach+0x1e/0x20
[ 43.655720] bus_add_driver+0x151/0x1f0
[ 43.655720] ? ehci_hcd_init+0xb2/0xb2
[ 43.655720] ? do_early_param+0x95/0x95
[ 43.655720] driver_register+0x70/0xc0
[ 43.655720] ? ehci_hcd_init+0xb2/0xb2
[ 43.655720] __pci_register_driver+0x57/0x60
[ 43.655720] ehci_pci_init+0x6a/0x6c
[ 43.655720] do_one_initcall+0x4a/0x1fa
[ 43.655720] ? do_early_param+0x95/0x95
[ 43.655720] kernel_init_freeable+0x1bd/0x262
[ 43.655720] ? rest_init+0xb0/0xb0
[ 43.655720] kernel_init+0xe/0x110
[ 43.655720] ret_from_fork+0x24/0x50

Fixes: 8af46c784ecfe ("iommu/vt-d: Implement is_attach_deferred iommu
ops entry")
Cc: stable@vger.kernel.org # v5.3+

Signed-off-by: John Donnelly <john.p.donnelly@oracle.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

---
drivers/iommu/intel-iommu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index c4e0e4a9ee9e..f83a9a302f8e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2783,7 +2783,7 @@ static int identity_mapping(struct device *dev)
struct device_domain_info *info;

info = dev->archdata.iommu;
- if (info && info != DUMMY_DEVICE_DOMAIN_INFO)
+ if (info && info != DUMMY_DEVICE_DOMAIN_INFO && info !=
DEFER_DEVICE_DOMAIN_INFO)
return (info->domain == si_domain);

return 0;
--
2.20.1

--
Thank You,
John