Re: [PATCH kernel v5 14/20] powerpc/powernv/npu: Add compound IOMMU groups

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 19/12/2018 11:17, Michael Ellerman wrote:
> Alexey Kardashevskiy <aik@ozlabs.ru> writes:
>> diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
>> index dc629ee..3468eaa 100644
>> --- a/arch/powerpc/platforms/powernv/npu-dma.c
>> +++ b/arch/powerpc/platforms/powernv/npu-dma.c
>> @@ -372,8 +358,263 @@ struct npu {
> ...
>> +
>> +static void pnv_comp_attach_table_group(struct npu_comp *npucomp,
>> +		struct pnv_ioda_pe *pe)
>> +{
>> +	if (WARN_ON(npucomp->pe_num == NV_NPU_MAX_PE_NUM))
>> +		return;
>> +
>> +	npucomp->pe[npucomp->pe_num] = pe;
>> +	++npucomp->pe_num;
>> +}
>> +
>> +struct iommu_table_group *pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
>> +{
>> +	struct iommu_table_group *table_group;
>> +	struct npu_comp *npucomp;
>> +	struct pci_dev *gpdev = NULL;
>> +	struct pci_controller *hose;
>> +	struct pci_dev *npdev;
>> +
>> +	list_for_each_entry(gpdev, &pe->pbus->devices, bus_list) {
>> +		npdev = pnv_pci_get_npu_dev(gpdev, 0);
>> +		if (npdev)
>> +			break;
>> +	}
>> +
>> +	if (!npdev)
>> +		/* It is not an NPU attached device, skip */
>> +		return NULL;
> 
> This breaks some configs with:
> 
>   arch/powerpc/platforms/powernv/npu-dma.c:550:5: error: 'npdev' may be used uninitialized in this function [-Werror=uninitialized]


gcc 5, 7 and 8 do not warn about this, I have to disable
list_for_each_entry() above to recreate this.

I even compiled gcc 5.5 which some of your buildmachines use and yet no
error on this:

make O=/home/aik/pbuild/kernel-le/ KCFLAGS=-Werror=all ARCH=powerpc
CROSS_COMPILE=/opt/cross/gcc-powerpc64le-linux-5.5.0-nolibc/bin/powerpc64le-linux-
arch/powerpc/platforms/powernv/npu-dma.o



I only get an error when I do:

@@ -525,6 +525,7 @@ struct iommu_table_group
*pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
        struct pci_controller *hose;
        struct pci_dev *npdev;

+       if (0)
        list_for_each_entry(gpdev, &pe->pbus->devices, bus_list) {

                npdev = pnv_pci_get_npu_dev(gpdev, 0);
                if (npdev)



How do you compile?


-- 
Alexey