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

[Kefeng Wang]

Hi Greg,

There are two more patches about the ZONE_DMA[32] changes, especially 
the second one, both them need be backported, thanks.

791ab8b2e3db - arm64: Ignore any DMA offsets in the max_zone_phys() 
calculation
2687275a5843 - arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation 
is required



On 2021/5/11 20:35, Kefeng Wang wrote:
> 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
> > .