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    SubjectRe: [PATCH stable v5.10 0/7] arm64: Default to 32-bit wide ZONE_DMA
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    On 2021/3/8 17:58, Greg KH wrote:
    > On Mon, Mar 08, 2021 at 11:20:03AM +0800, Jing Xiangfeng wrote:
    >>
    >>
    >> 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, now queued up.

    Hi Grep, another commit d78050ee3544 "arm64: Remove
    arm64_dma32_phys_limit and its uses" should be involved, thanks.

    "Prior to this patch, disabling CONFIG_ZONE_DMA32 leads to CMA
    allocation from the whole RAM as arm64_dma32_phys_limit becomes
    PHYS_MASK+1." from Catalin, see more from the link
    https://www.spinics.net/lists/arm-kernel/msg867356.html
    >
    > greg k-h
    > .
    >

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