[PATCH] powerpc/iommu: fix lockdep warning during PCI enumeration

[Nilay Shroff <nilay@linux.ibm.com>]

Commit a75b2be249d6 ("iommu: Add iommu_driver_get_domain_for_dev()
helper") introduced iommu_driver_get_domain_for_dev() for driver
code paths that hold iommu_group->mutex while attaching a device
to an IOMMU domain.

The same commit also added a lockdep assertion in
iommu_get_domain_for_dev() to ensure that callers do not hold
iommu_group->mutex when invoking it.

On powerpc platforms, when PCI device ownership is switched from
BLOCKED to the PLATFORM domain, the attach callback
spapr_tce_platform_iommu_attach_dev() still calls
iommu_get_domain_for_dev(). This happens while iommu_group->mutex
is held during domain switching, which triggers the lockdep warning
below during PCI enumeration:

WARNING: drivers/iommu/iommu.c:2252 at iommu_get_domain_for_dev+0x38/0x80, CPU#2: swapper/0/1
Modules linked in:
CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc2+ #35 PREEMPT
Hardware name: IBM,9105-22A Power11 (architected) 0x820200 0xf000007 of:IBM,FW1120.00 (RB1120_115) hv:phyp pSeries
NIP:  c000000000c244c4 LR: c00000000005b5a4 CTR: c00000000005b578
REGS: c00000000a7bf280 TRAP: 0700   Not tainted  (7.0.0-rc2+)
MSR:  8000000002029033 <SF,VEC,EE,ME,IR,DR,RI,LE>  CR: 22004422  XER: 0000000a
CFAR: c000000000c24508 IRQMASK: 0
GPR00: c00000000005b5a4 c00000000a7bf520 c000000001dc8100 0000000000000001
GPR04: c00000000f972f10 0000000000000000 0000000000000000 0000000000000001
GPR08: 0000001ffbc60000 0000000000000001 0000000000000000 0000000000000000
GPR12: c00000000005b578 c000001fffffe480 c000000000011618 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: ffffffffffffefff 0000000000000000 c000000002d30eb0 0000000000000001
GPR24: c0000000017881f8 0000000000000000 0000000000000001 c00000000f972e00
GPR28: c00000000bbba0d0 0000000000000000 c00000000bbba0d0 c00000000f972e00
NIP [c000000000c244c4] iommu_get_domain_for_dev+0x38/0x80
LR [c00000000005b5a4] spapr_tce_platform_iommu_attach_dev+0x2c/0x98
Call Trace:
 iommu_get_domain_for_dev+0x68/0x80 (unreliable)
 spapr_tce_platform_iommu_attach_dev+0x2c/0x98
 __iommu_attach_device+0x44/0x220
 __iommu_device_set_domain+0xf4/0x194
 __iommu_group_set_domain_internal+0xec/0x228
 iommu_setup_default_domain+0x5f4/0x6a4
 __iommu_probe_device+0x674/0x724
 iommu_probe_device+0x50/0xb4
 iommu_add_device+0x48/0x198
 pci_dma_dev_setup_pSeriesLP+0x198/0x4f0
 pcibios_bus_add_device+0x80/0x464
 pci_bus_add_device+0x40/0x100
 pci_bus_add_devices+0x54/0xb0
 pcibios_init+0xd8/0x140
 do_one_initcall+0x8c/0x598
 kernel_init_freeable+0x3ec/0x850
 kernel_init+0x34/0x270
 ret_from_kernel_user_thread+0x14/0x1c

Fix this by using iommu_driver_get_domain_for_dev() instead of
iommu_get_domain_for_dev() in spapr_tce_platform_iommu_attach_dev(),
which is the appropriate helper for callers holding the group mutex.

Cc: stable@vger.kernel.org
Fixes: a75b2be249d6 ("iommu: Add iommu_driver_get_domain_for_dev() helper")
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 arch/powerpc/kernel/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 0ce71310b7d9..d122e8447831 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1159,7 +1159,7 @@ spapr_tce_platform_iommu_attach_dev(struct iommu_domain *platform_domain,
 				    struct device *dev,
 				    struct iommu_domain *old)
 {
-	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
+	struct iommu_domain *domain = iommu_driver_get_domain_for_dev(dev);
 	struct iommu_table_group *table_group;
 	struct iommu_group *grp;
 
-- 
2.53.0