powerpc/powernv/sriov: Register IOMMU groups for VFs

The compound IOMMU group rework moved iommu_register_group() together
in pnv_pci_ioda_setup_iommu_api() (which is a part of
ppc_md.pcibios_fixup). As the result, pnv_ioda_setup_bus_iommu_group()
does not create groups any more, it only adds devices to groups.

This works fine for boot time devices. However IOMMU groups for
SRIOV's VFs were added by pnv_ioda_setup_bus_iommu_group() so this got
broken: pnv_tce_iommu_bus_notifier() expects a group to be registered
for VF and it is not.

This adds missing group registration and adds a NULL pointer check
into the bus notifier so we won't crash if there is no group, although
it is not expected to happen now because of the change above.

Example oops seen prior to this patch:

$ echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/sriov_numvfs
Unable to handle kernel paging request for data at address 0x00000030
Faulting instruction address: 0xc0000000004a6018
Oops: Kernel access of bad area, sig: 11 [#1]
LE SMP NR_CPUS=2048 NUMA PowerNV
CPU: 46 PID: 7006 Comm: bash Not tainted 4.15-ish
NIP: c0000000004a6018 LR: c0000000004a6014 CTR: 0000000000000000
REGS: c000008fc876b400 TRAP: 0300 Not tainted (4.15-ish)
MSR: 900000000280b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>
CFAR: c000000000d0be20 DAR: 0000000000000030 DSISR: 40000000 SOFTE: 1
...
NIP sysfs_do_create_link_sd.isra.0+0x68/0x150
LR sysfs_do_create_link_sd.isra.0+0x64/0x150
Call Trace:
pci_dev_type+0x0/0x30 (unreliable)
iommu_group_add_device+0x8c/0x600
iommu_add_device+0xe8/0x180
pnv_tce_iommu_bus_notifier+0xb0/0xf0
notifier_call_chain+0x9c/0x110
blocking_notifier_call_chain+0x64/0xa0
device_add+0x524/0x7d0
pci_device_add+0x248/0x450
pci_iov_add_virtfn+0x294/0x3e0
pci_enable_sriov+0x43c/0x580
mlx5_core_sriov_configure+0x15c/0x2f0 [mlx5_core]
sriov_numvfs_store+0x180/0x240
dev_attr_store+0x3c/0x60
sysfs_kf_write+0x64/0x90
kernfs_fop_write+0x1ac/0x240
__vfs_write+0x3c/0x70
vfs_write+0xd8/0x220
SyS_write+0x6c/0x110
system_call+0x58/0x6c

Fixes: 0bd971676e68 ("powerpc/powernv/npu: Add compound IOMMU groups")
Signed-off-by: Alexey Kardashevskiy <[e-mail]>
Reported-by: Santwana Samantray <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

arch/powerpc/platforms/powernv/pci-ioda.c

···
 
 		pnv_pci_ioda2_setup_dma_pe(phb, pe);
 #ifdef CONFIG_IOMMU_API
+		iommu_register_group(&pe->table_group,
+				pe->phb->hose->global_number, pe->pe_number);
 		pnv_ioda_setup_bus_iommu_group(pe, &pe->table_group, NULL);
 #endif
 	}

arch/powerpc/platforms/powernv/pci.c

···
 			return 0;
 
 		pe = &phb->ioda.pe_array[pdn->pe_number];
+		if (!pe->table_group.group)
+			return 0;
 		iommu_add_device(&pe->table_group, dev);
 		return 0;
 	case BUS_NOTIFY_DEL_DEVICE: