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

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Date:   Wed, 12 May 2021 14:06:15 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Jing Xiangfeng <jingxiangfeng@...wei.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        catalin.marinas@....com, will@...nel.org,
        akpm@...ux-foundation.org, paul.walmsley@...ive.com,
        palmer@...belt.com, aou@...s.berkeley.edu, rppt@...nel.org,
        lorenzo.pieralisi@....com, guohanjun@...wei.com,
        sudeep.holla@....com, rjw@...ysocki.net, lenb@...nel.org,
        song.bao.hua@...ilicon.com, ardb@...nel.org,
        anshuman.khandual@....com, bhelgaas@...gle.com, guro@...com,
        robh+dt@...nel.org, stable@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, frowand.list@...il.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH stable v5.10 0/7] arm64: Default to 32-bit wide ZONE_DMA

On Tue, May 11, 2021 at 08:35:47PM +0800, 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

Ok, now queued up.

greg k-h