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Date:   Wed, 12 May 2021 14:06:15 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Kefeng Wang <wangkefeng.wang@huawei.com>
Cc:     Jing Xiangfeng <jingxiangfeng@huawei.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        catalin.marinas@arm.com, will@kernel.org,
        akpm@linux-foundation.org, paul.walmsley@sifive.com,
        palmer@dabbelt.com, aou@eecs.berkeley.edu, rppt@kernel.org,
        lorenzo.pieralisi@arm.com, guohanjun@huawei.com,
        sudeep.holla@arm.com, rjw@rjwysocki.net, lenb@kernel.org,
        song.bao.hua@hisilicon.com, ardb@kernel.org,
        anshuman.khandual@arm.com, bhelgaas@google.com, guro@fb.com,
        robh+dt@kernel.org, stable@vger.kernel.org,
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        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-riscv@lists.infradead.org
Subject: Re: [PATCH stable v5.10 0/7] arm64: Default to 32-bit wide ZONE_DMA
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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