[PATCH kernel 1/2] powerpc/powernv: Fix insufficient memory allocation

[Alexey Kardashevskiy]

On 05/12/2016 04:09 PM, Gavin Shan wrote:
> On Thu, May 12, 2016 at 03:47:09PM +1000, Alexey Kardashevskiy wrote:
>> The pnv_pci_init_ioda_phb() helper allocates a blob to store auxilary
>> data such PE and M32/M64 segment allocation maps; this single blob has few
>> partitions, size of each is derived from the PE number -
>> phb->ioda.total_pe_num.
>>
>> It was assumed that the minimum PE number is 8, however it is 4 for NPU
>> so the pe_alloc part was missing in the allocated blob.
>> It was invisible till recently as we were not tracking used M64 segments
>> and NPUs do not use M32 segments so the phb->ioda.m32_segmap
>> (which was pointing to the same address as phb->ioda.pe_alloc)
>> has never been written to leaving the pe_alloc memory intact.
>>
>> After 401203ac2d "powerpc/powernv: Track M64 segment consumption"
>> the pe_alloc gets corrupted and PE allocation cannot work.
>> This fixes the issue by enforcing the minimum PE number to 8.
>>
>
> As I said offline yesterday, the issue exists from day-1 when NPU PHB
> is supported. I don't think it's related to 401203ac2d. Without the logic
> tracking M64 segments, the PE# bitmap still can be corrupted when writting
> to M32 segment map. It's confusing to mention a unrelated commit in the
> changelog.


The bug exists from day 1. The actual corruption started happening from 
401203ac2d, it could be happening before but it was not.

>
> Since the issue exists from day-1 when NPU PHB is supported, is a stable
> tag needed?
>
>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>
> With above parts fixed:
>
> Reviewed-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
>
>> ---
>> 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 6cda2a8..d0d32c2 100644
>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>> @@ -3507,7 +3507,8 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>> 				PNV_IODA1_DMA32_SEGSIZE;
>>
>> 	/* Allocate aux data & arrays. We don't have IO ports on PHB3 */
>> -	size = _ALIGN_UP(phb->ioda.total_pe_num / 8, sizeof(unsigned long));
>> +	size = _ALIGN_UP(max_t(unsigned, phb->ioda.total_pe_num, 8) / 8,
>> +			sizeof(unsigned long));
>> 	m64map_off = size;
>> 	size += phb->ioda.total_pe_num * sizeof(phb->ioda.m64_segmap[0]);
>> 	m32map_off = size;
>> --
>> 2.5.0.rc3
>>
>


-- 
Alexey