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

From: Gavin Shan <[email-masked]>
Date: Thu, 12 May 2016 16:59:51 +1000

On Thu, May 12, 2016 at 04:39:57PM +1000, Alexey Kardashevskiy wrote:
>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.
>

well, Are you sure it starts from 401203ac2d? I would believe it starts
from commit 3fa23ff ("powerpc/powernv: Fix initial IO and M32 segmap").
Please fix the commit log.

>>
>>Since the issue exists from day-1 when NPU PHB is supported, is a stable
>>tag needed?
>>
>>>Signed-off-by: Alexey Kardashevskiy <[email-masked]>
>>
>>With above parts fixed:
>>
>>Reviewed-by: Gavin Shan <[email-masked]>
>>
>>>---
>>>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
>