Re: [PATCH] powerpc/powernv/npu: Fix oops in pnv_try_setup_npu_table_group()

[Frederic Barrat <fbarrat@linux.ibm.com>]

Le 09/01/2019 à 17:25, Greg Kurz a écrit :
> On Wed,  9 Jan 2019 16:13:42 +0100
> Frederic Barrat <fbarrat@linux.ibm.com> wrote:
> 
>> With a recent change around IOMMU group, a system with an opencapi
>> adapter is no longer booting and we get a kernel oops:
>>
>> BUG: Kernel NULL pointer dereference at 0x00000028
>> Faulting instruction address: 0xc0000000000aa38c
>> Oops: Kernel access of bad area, sig: 7 [#1]
>> LE SMP NR_CPUS=2048 NUMA PowerNV
>> Modules linked in:
>> CPU: 5 PID: 1 Comm: swapper/4 Not tainted 5.0.0-rc1-fxb-00001-g3bd6e94bec12
>> NIP:  c0000000000aa38c LR: c0000000000a6608 CTR: c000000000097480
>> REGS: c000000005783700 TRAP: 0300   Not tainted  (5.0.0-rc1-fxb-00001-g3bd6
>> MSR:  9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 28000228  XER: 20
>> CFAR: c0000000000a6604 DAR: 0000000000000028 DSISR: 00080000 IRQMASK: 0
>> GPR00: c0000000000a6608 c000000005783990 c000000001036100 c0000007bf761860
>> GPR04: 0000000000000000 c000000005783834 0000000000000000 0000000000000000
>> GPR08: 69626d2c6e707500 0000000000000000 0000000000000000 9000000002001003
>> GPR12: 0000000000000000 c0000007bfff8300 c000000000010450 0000000000000000
>> GPR16: c000000000ced938 0000000000000100 c000000000ced948 00000000000a0000
>> GPR20: 00000000000bfffe c000000000ced9a8 0000000000000200 c000000000ced978
>> GPR24: 00000000006080c0 c000000716d09828 c00000002e6fd000 0000000000000000
>> GPR28: c0000007bf4aff68 c0000007bf8d0080 c000000000f23938 c0000007bf761860
>> NIP [c0000000000aa38c] pnv_try_setup_npu_table_group+0x1c/0x1a0
>> LR [c0000000000a6608] pnv_pci_ioda_fixup+0x1f8/0x660
>> Call Trace:
>> [c000000005783990] [c0000000000aa3d0] pnv_try_setup_npu_table_group+0x60/0x
>> [c0000000057839d0] [c0000000000a661c] pnv_pci_ioda_fixup+0x20c/0x660
>> [c000000005783ab0] [c000000000e1d4c0] pcibios_resource_survey+0x2c8/0x31c
>> [c000000005783b90] [c000000000e1caf4] pcibios_init+0xb0/0xe4
>> [c000000005783c10] [c000000000010054] do_one_initcall+0x64/0x264
>> [c000000005783ce0] [c000000000e1132c] kernel_init_freeable+0x36c/0x468
>> [c000000005783db0] [c000000000010474] kernel_init+0x2c/0x148
>> [c000000005783e20] [c00000000000b794] ret_from_kernel_thread+0x5c/0x68
>>
>> An opencapi device is using a device PE, so the current code breaks
>> because pe->pbus is not defined.
>>
>> More generally, there's no need to define an IOMMU group for opencapi,
>> as the device sends real addresses directly (admittedly, the
>> virtualization story is yet to be written). So let's fix it by
> 
> Current plan is to go for mediated VFIO. The real HW stays under the control
> of the host ocxl driver, and we still don't need an IOMMU group.
> 
>> skipping the IOMMU group setup for opencapi PHBs.
>>
>> Fixes: 0bd971676e68 ("powerpc/powernv/npu: Add compound IOMMU groups")
>> Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
>> ---
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>
> 
> and
> 
> Cc: stable@vger.kernel.org      # v4.20

Thanks for the review! But why did you add stable? that problem is only 
seen on 5.0-rc1, isn't it?

   Fred


>>   arch/powerpc/platforms/powernv/pci-ioda.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>> index 1d6406a051f1..7db3119f8a5b 100644
>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>> @@ -2681,7 +2681,8 @@ static void pnv_pci_ioda_setup_iommu_api(void)
>>   	list_for_each_entry(hose, &hose_list, list_node) {
>>   		phb = hose->private_data;
>>   
>> -		if (phb->type == PNV_PHB_NPU_NVLINK)
>> +		if (phb->type == PNV_PHB_NPU_NVLINK ||
>> +		    phb->type == PNV_PHB_NPU_OCAPI)
>>   			continue;
>>   
>>   		list_for_each_entry(pe, &phb->ioda.pe_list, list) {
>