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. That said, I have no clue whether this falls or not into the stable kernel rules. Regards, Nicolas
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