[PATCH stable v5.10 0/7] arm64: Default to 32-bit wide ZONE_DMA

[Jing Xiangfeng]

On 2021/3/7 23:24, Greg KH wrote:
> On Thu, Mar 04, 2021 at 04:09:28PM +0100, Nicolas Saenz Julienne wrote:
>> On Thu, 2021-03-04 at 15:17 +0100, Greg KH wrote:
>>> On Thu, Mar 04, 2021 at 03:05:32PM +0100, Nicolas Saenz Julienne wrote:
>>>> Hi Greg.
>>>>
>>>> On Thu, 2021-03-04 at 14:46 +0100, Greg KH wrote:
>>>>> On Wed, Mar 03, 2021 at 03:33:12PM +0800, Jing Xiangfeng wrote:
>>>>>> Using two distinct DMA zones turned out to be problematic. Here's an
>>>>>> attempt go back to a saner default.
>>>>> What problem does this solve?  How does this fit into the stable kernel
>>>>> rules?
>>>> We changed the way we setup memory zones in arm64 in order to cater for
>>>> Raspberry Pi 4's weird DMA constraints: ZONE_DMA spans the lower 1GB of memory
>>>> and ZONE_DMA32 the rest of the 32bit address space. Since you can't allocate
>>>> memory that crosses zone boundaries, this broke crashkernel allocations on big
>>>> machines. This series fixes all this by parsing the HW description and checking
>>>> for DMA constrained buses. When not found, the unnecessary zone creation is
>>>> skipped.
>>> What kernel/commit caused this "breakage"?
>> 1a8e1cef7603 arm64: use both ZONE_DMA and ZONE_DMA32
> Thanks for the info, all now queued up.
There is a fix in 5.11. Please consider applying the following commit to 
5.10.y:

aed5041ef9a3 of: unittest: Fix build on architectures without 
CONFIG_OF_ADDRES

Thanks

>
> greg k-h
> .
>