Date:   Fri, 19 Jun 2020 19:01:14 -0500
From:   John Donnelly <john.p.donnelly@...cle.com>
To:     chenzhou <chenzhou10@...wei.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Bhupesh Sharma <bhsharma@...hat.com>
Cc:     Simon Horman <horms@...ge.net.au>,
        Devicetree List <devicetree@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Baoquan He <bhe@...hat.com>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        guohanjun@...wei.com,
        kexec mailing list <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        James Morse <james.morse@....com>,
        Prabhakar Kushwaha <prabhakar.pkin@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Prabhakar Kushwaha <pkushwaha@...vell.com>,
        RuiRui Yang <dyoung@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 0/5] support reserving crashkernel above 4G on arm64
 kdump


On 6/19/20 3:21 AM, chenzhou wrote:
> On 2020/6/19 10:32, John Donnelly wrote:
>> On 6/4/20 12:01 PM, Nicolas Saenz Julienne wrote:
>>> On Thu, 2020-06-04 at 01:17 +0530, Bhupesh Sharma wrote:
>>>> Hi All,
>>>>
>>>> On Wed, Jun 3, 2020 at 9:03 PM John Donnelly <john.p.donnelly@...cle.com>
>>>> wrote:
>>>>>> On Jun 3, 2020, at 8:20 AM, chenzhou <chenzhou10@...wei.com> wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>>
>>>>>> On 2020/6/3 19:47, Prabhakar Kushwaha wrote:
>>>>>>> Hi Chen,
>>>>>>>
>>>>>>> On Tue, Jun 2, 2020 at 8:12 PM John Donnelly <john.p.donnelly@...cle.com
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> On Jun 2, 2020, at 12:38 AM, Prabhakar Kushwaha <
>>>>>>>>> prabhakar.pkin@...il.com> wrote:
>>>>>>>>>
>>>>>>>>> On Tue, Jun 2, 2020 at 3:29 AM John Donnelly <
>>>>>>>>> john.p.donnelly@...cle.com> wrote:
>>>>>>>>>> Hi .  See below !
>>>>>>>>>>
>>>>>>>>>>> On Jun 1, 2020, at 4:02 PM, Bhupesh Sharma <bhsharma@...hat.com>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>> Hi John,
>>>>>>>>>>>
>>>>>>>>>>> On Tue, Jun 2, 2020 at 1:01 AM John Donnelly <
>>>>>>>>>>> John.P.donnelly@...cle.com> wrote:
>>>>>>>>>>>> Hi,
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On 6/1/20 7:02 AM, Prabhakar Kushwaha wrote:
>>>>>>>>>>>>> Hi Chen,
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, May 21, 2020 at 3:05 PM Chen Zhou <
>>>>>>>>>>>>> chenzhou10@...wei.com> wrote:
>>>>>>>>>>>>>> This patch series enable reserving crashkernel above 4G in
>>>>>>>>>>>>>> arm64.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> There are following issues in arm64 kdump:
>>>>>>>>>>>>>> 1. We use crashkernel=X to reserve crashkernel below 4G,
>>>>>>>>>>>>>> which will fail
>>>>>>>>>>>>>> when there is no enough low memory.
>>>>>>>>>>>>>> 2. Currently, crashkernel=Y@X can be used to reserve
>>>>>>>>>>>>>> crashkernel above 4G,
>>>>>>>>>>>>>> in this case, if swiotlb or DMA buffers are required,
>>>>>>>>>>>>>> crash dump kernel
>>>>>>>>>>>>>> will boot failure because there is no low memory available
>>>>>>>>>>>>>> for allocation.
>>>>>>>>>>>>>>
>>>>>>>>>>>>> We are getting "warn_alloc" [1] warning during boot of kdump
>>>>>>>>>>>>> kernel
>>>>>>>>>>>>> with bootargs as [2] of primary kernel.
>>>>>>>>>>>>> This error observed on ThunderX2  ARM64 platform.
>>>>>>>>>>>>>
>>>>>>>>>>>>> It is observed with latest upstream tag (v5.7-rc3) with this
>>>>>>>>>>>>> patch set
>>>>>>>>>>>>> and
>>>>>>>>>>>>>
>>> https://urldefense.com/v3/__https://lists.infradead.org/pipermail/kexec/2020-May/025128.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbiIAAlzu$
>>>>>>>>>>>>> Also **without** this patch-set
>>>>>>>>>>>>> "
>>>>>>>>>>>>>
>>> https://urldefense.com/v3/__https://www.spinics.net/lists/arm-kernel/msg806882.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbjC6ujMA$
>>>>>>>>>>>>> "
>>>>>>>>>>>>>
>>>>>>>>>>>>> This issue comes whenever crashkernel memory is reserved
>>>>>>>>>>>>> after 0xc000_0000.
>>>>>>>>>>>>> More details discussed earlier in
>>>>>>>>>>>>>
>>> https://urldefense.com/v3/__https://www.spinics.net/lists/arm-kernel/msg806882.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbjC6ujMA$
>>>     without
>>>>>>>>>>>>> any
>>>>>>>>>>>>> solution
>>>>>>>>>>>>>
>>>>>>>>>>>>> This patch-set is expected to solve similar kind of issue.
>>>>>>>>>>>>> i.e. low memory is only targeted for DMA, swiotlb; So above
>>>>>>>>>>>>> mentioned
>>>>>>>>>>>>> observation should be considered/fixed. .
>>>>>>>>>>>>>
>>>>>>>>>>>>> --pk
>>>>>>>>>>>>>
>>>>>>>>>>>>> [1]
>>>>>>>>>>>>> [   30.366695] DMI: Cavium Inc. Saber/Saber, BIOS
>>>>>>>>>>>>> TX2-FW-Release-3.1-build_01-2803-g74253a541a mm/dd/yyyy
>>>>>>>>>>>>> [   30.367696] NET: Registered protocol family 16
>>>>>>>>>>>>> [   30.369973] swapper/0: page allocation failure: order:6,
>>>>>>>>>>>>> mode:0x1(GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
>>>>>>>>>>>>> [   30.369980] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
>>>>>>>>>>>>> 5.7.0-rc3+ #121
>>>>>>>>>>>>> [   30.369981] Hardware name: Cavium Inc. Saber/Saber, BIOS
>>>>>>>>>>>>> TX2-FW-Release-3.1-build_01-2803-g74253a541a mm/dd/yyyy
>>>>>>>>>>>>> [   30.369984] Call trace:
>>>>>>>>>>>>> [   30.369989]  dump_backtrace+0x0/0x1f8
>>>>>>>>>>>>> [   30.369991]  show_stack+0x20/0x30
>>>>>>>>>>>>> [   30.369997]  dump_stack+0xc0/0x10c
>>>>>>>>>>>>> [   30.370001]  warn_alloc+0x10c/0x178
>>>>>>>>>>>>> [   30.370004]  __alloc_pages_slowpath.constprop.111+0xb10/0
>>>>>>>>>>>>> xb50
>>>>>>>>>>>>> [   30.370006]  __alloc_pages_nodemask+0x2b4/0x300
>>>>>>>>>>>>> [   30.370008]  alloc_page_interleave+0x24/0x98
>>>>>>>>>>>>> [   30.370011]  alloc_pages_current+0xe4/0x108
>>>>>>>>>>>>> [   30.370017]  dma_atomic_pool_init+0x44/0x1a4
>>>>>>>>>>>>> [   30.370020]  do_one_initcall+0x54/0x228
>>>>>>>>>>>>> [   30.370027]  kernel_init_freeable+0x228/0x2cc
>>>>>>>>>>>>> [   30.370031]  kernel_init+0x1c/0x110
>>>>>>>>>>>>> [   30.370034]  ret_from_fork+0x10/0x18
>>>>>>>>>>>>> [   30.370036] Mem-Info:
>>>>>>>>>>>>> [   30.370064] active_anon:0 inactive_anon:0 isolated_anon:0
>>>>>>>>>>>>> [   30.370064]  active_file:0 inactive_file:0
>>>>>>>>>>>>> isolated_file:0
>>>>>>>>>>>>> [   30.370064]  unevictable:0 dirty:0 writeback:0 unstable:0
>>>>>>>>>>>>> [   30.370064]  slab_reclaimable:34 slab_unreclaimable:4438
>>>>>>>>>>>>> [   30.370064]  mapped:0 shmem:0 pagetables:14 bounce:0
>>>>>>>>>>>>> [   30.370064]  free:1537719 free_pcp:219 free_cma:0
>>>>>>>>>>>>> [   30.370070] Node 0 active_anon:0kB inactive_anon:0kB
>>>>>>>>>>>>> active_file:0kB inactive_file:0kB unevictable:0kB
>>>>>>>>>>>>> isolated(anon):0kB
>>>>>>>>>>>>> isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB
>>>>>>>>>>>>> shmem:0kB
>>>>>>>>>>>>> shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB
>>>>>>>>>>>>> writeback_tmp:0kB
>>>>>>>>>>>>> unstable:0kB all_unreclaimable? no
>>>>>>>>>>>>> [   30.370073] Node 1 active_anon:0kB inactive_anon:0kB
>>>>>>>>>>>>> active_file:0kB inactive_file:0kB unevictable:0kB
>>>>>>>>>>>>> isolated(anon):0kB
>>>>>>>>>>>>> isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB
>>>>>>>>>>>>> shmem:0kB
>>>>>>>>>>>>> shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB
>>>>>>>>>>>>> writeback_tmp:0kB
>>>>>>>>>>>>> unstable:0kB all_unreclaimable? no
>>>>>>>>>>>>> [   30.370079] Node 0 DMA free:0kB min:0kB low:0kB high:0kB
>>>>>>>>>>>>> reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB
>>>>>>>>>>>>> active_file:0kB inactive_file:0kB unevictable:0kB
>>>>>>>>>>>>> writepending:0kB
>>>>>>>>>>>>> present:128kB managed:0kB mlocked:0kB kernel_stack:0kB
>>>>>>>>>>>>> pagetables:0kB
>>>>>>>>>>>>> bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
>>>>>>>>>>>>> [   30.370084] lowmem_reserve[]: 0 250 6063 6063
>>>>>>>>>>>>> [   30.370090] Node 0 DMA32 free:256000kB min:408kB
>>>>>>>>>>>>> low:664kB
>>>>>>>>>>>>> high:920kB reserved_highatomic:0KB active_anon:0kB
>>>>>>>>>>>>> inactive_anon:0kB
>>>>>>>>>>>>> active_file:0kB inactive_file:0kB unevictable:0kB
>>>>>>>>>>>>> writepending:0kB
>>>>>>>>>>>>> present:269700kB managed:256000kB mlocked:0kB
>>>>>>>>>>>>> kernel_stack:0kB
>>>>>>>>>>>>> pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB
>>>>>>>>>>>>> free_cma:0kB
>>>>>>>>>>>>> [   30.370094] lowmem_reserve[]: 0 0 5813 5813
>>>>>>>>>>>>> [   30.370100] Node 0 Normal free:5894876kB min:9552kB
>>>>>>>>>>>>> low:15504kB
>>>>>>>>>>>>> high:21456kB reserved_highatomic:0KB active_anon:0kB
>>>>>>>>>>>>> inactive_anon:0kB
>>>>>>>>>>>>> active_file:0kB inactive_file:0kB unevictable:0kB
>>>>>>>>>>>>> writepending:0kB
>>>>>>>>>>>>> present:8388608kB managed:5953112kB mlocked:0kB
>>>>>>>>>>>>> kernel_stack:21672kB
>>>>>>>>>>>>> pagetables:56kB bounce:0kB free_pcp:876kB local_pcp:176kB
>>>>>>>>>>>>> free_cma:0kB
>>>>>>>>>>>>> [   30.370104] lowmem_reserve[]: 0 0 0 0
>>>>>>>>>>>>> [   30.370107] Node 0 DMA: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB
>>>>>>>>>>>>> 0*128kB
>>>>>>>>>>>>> 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0kB
>>>>>>>>>>>>> [   30.370113] Node 0 DMA32: 0*4kB 0*8kB 0*16kB 0*32kB
>>>>>>>>>>>>> 0*64kB 0*128kB
>>>>>>>>>>>>> 0*256kB 0*512kB 0*1024kB 1*2048kB (M) 62*4096kB (M) =
>>>>>>>>>>>>> 256000kB
>>>>>>>>>>>>> [   30.370119] Node 0 Normal: 2*4kB (M) 3*8kB (ME) 2*16kB
>>>>>>>>>>>>> (UE) 3*32kB
>>>>>>>>>>>>> (UM) 1*64kB (U) 2*128kB (M) 2*256kB (ME) 3*512kB (ME)
>>>>>>>>>>>>> 3*1024kB (ME)
>>>>>>>>>>>>> 3*2048kB (UME) 1436*4096kB (M) = 5893600kB
>>>>>>>>>>>>> [   30.370129] Node 0 hugepages_total=0 hugepages_free=0
>>>>>>>>>>>>> hugepages_surp=0 hugepages_size=1048576kB
>>>>>>>>>>>>> [   30.370130] 0 total pagecache pages
>>>>>>>>>>>>> [   30.370132] 0 pages in swap cache
>>>>>>>>>>>>> [   30.370134] Swap cache stats: add 0, delete 0, find 0/0
>>>>>>>>>>>>> [   30.370135] Free swap  = 0kB
>>>>>>>>>>>>> [   30.370136] Total swap = 0kB
>>>>>>>>>>>>> [   30.370137] 2164609 pages RAM
>>>>>>>>>>>>> [   30.370139] 0 pages HighMem/MovableOnly
>>>>>>>>>>>>> [   30.370140] 612331 pages reserved
>>>>>>>>>>>>> [   30.370141] 0 pages hwpoisoned
>>>>>>>>>>>>> [   30.370143] DMA: failed to allocate 256 KiB pool for
>>>>>>>>>>>>> atomic
>>>>>>>>>>>>> coherent allocation
>>>>>>>>>>>> During my testing I saw the same error and Chen's  solution
>>>>>>>>>>>> corrected it .
>>>>>>>>>>> Which combination you are using on your side? I am using
>>>>>>>>>>> Prabhakar's
>>>>>>>>>>> suggested environment and can reproduce the issue
>>>>>>>>>>> with or without Chen's crashkernel support above 4G patchset.
>>>>>>>>>>>
>>>>>>>>>>> I am also using a ThunderX2 platform with latest makedumpfile
>>>>>>>>>>> code and
>>>>>>>>>>> kexec-tools (with the suggested patch
>>>>>>>>>>> <
>>>>>>>>>>>
>>> https://urldefense.com/v3/__https://lists.infradead.org/pipermail/kexec/2020-May/025128.html__;!!GqivPVa7Brio!J6lUig58-Gw6TKZnEEYzEeSU36T-1SqlB1kImU00xtX_lss5Tx-JbUmLE9TJC3foXBLg$
>>>>>>>>>>>> ).
>>>>>>>>>>> Thanks,
>>>>>>>>>>> Bhupesh
>>>>>>>>>> I did this activity 5 months ago and I have moved on to other
>>>>>>>>>> activities. My DMA failures were related to PCI devices that could
>>>>>>>>>> not be enumerated because  low-DMA space was not  available when
>>>>>>>>>> crashkernel was moved above 4G; I don’t recall the exact platform.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> For this failure ,
>>>>>>>>>>
>>>>>>>>>>>>> DMA: failed to allocate 256 KiB pool for atomic
>>>>>>>>>>>>> coherent allocation
>>>>>>>>>> Is due to :
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 3618082c
>>>>>>>>>> ("arm64 use both ZONE_DMA and ZONE_DMA32")
>>>>>>>>>>
>>>>>>>>>> With the introduction of ZONE_DMA to support the Raspberry DMA
>>>>>>>>>> region below 1G, the crashkernel is placed in the upper 4G
>>>>>>>>>> ZONE_DMA_32 region. Since the crashkernel does not have access
>>>>>>>>>> to the ZONE_DMA region, it prints out call trace during bootup.
>>>>>>>>>>
>>>>>>>>>> It is due to having this CONFIG item  ON  :
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> CONFIG_ZONE_DMA=y
>>>>>>>>>>
>>>>>>>>>> Turning off ZONE_DMA fixes a issue and Raspberry PI 4 will
>>>>>>>>>> use the device tree to specify memory below 1G.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> Disabling ZONE_DMA is temporary solution.  We may need proper
>>>>>>>>> solution
>>>>>>>> Perhaps the Raspberry platform configuration dependencies need
>>>>>>>> separated  from “server class” Arm  equipment ?  Or auto-configured on
>>>>>>>> boot ?  Consult an expert ;-)
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>> I would like to see Chen’s feature added , perhaps as
>>>>>>>>>> EXPERIMENTAL,  so we can get some configuration testing done on
>>>>>>>>>> it.   It corrects having a DMA zone in low memory while crash-
>>>>>>>>>> kernel is above 4GB.  This has been going on for a year now.
>>>>>>>>> I will also like this patch to be added in Linux as early as
>>>>>>>>> possible.
>>>>>>>>>
>>>>>>>>> Issue mentioned by me happens with or without this patch.
>>>>>>>>>
>>>>>>>>> This patch-set can consider fixing because it uses low memory for
>>>>>>>>> DMA
>>>>>>>>> & swiotlb only.
>>>>>>>>> We can consider restricting crashkernel within the required range
>>>>>>>>> like below
>>>>>>>>>
>>>>>>>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>>>>>>>>> index 7f9e5a6dc48c..bd67b90d35bd 100644
>>>>>>>>> --- a/kernel/crash_core.c
>>>>>>>>> +++ b/kernel/crash_core.c
>>>>>>>>> @@ -354,7 +354,7 @@ int __init reserve_crashkernel_low(void)
>>>>>>>>>                         return 0;
>>>>>>>>>         }
>>>>>>>>>
>>>>>>>>> -       low_base = memblock_find_in_range(0, 1ULL << 32, low_size,
>>>>>>>>> CRASH_ALIGN);
>>>>>>>>> +       low_base = memblock_find_in_range(0,0xc0000000, low_size,
>>>>>>>>> CRASH_ALIGN);
>>>>>>>>>         if (!low_base) {
>>>>>>>>>                 pr_err("Cannot reserve %ldMB crashkernel low memory,
>>>>>>>>> please try smaller size.\n",
>>>>>>>>>                        (unsigned long)(low_size >> 20));
>>>>>>>>>
>>>>>>>>>
>>>>>>>>      I suspect  0xc0000000  would need to be a CONFIG item  and not
>>>>>>>> hard-coded.
>>>>>>>>
>>>>>>> if you consider this as valid change,  can you please incorporate as
>>>>>>> part of your patch-set.
>>>>>> After commit 1a8e1cef7 ("arm64: use both ZONE_DMA and ZONE_DMA32")，the 0-
>>>>>> 4G memory is splited
>>>>>> to DMA [mem 0x0000000000000000-0x000000003fffffff] and DMA32 [mem
>>>>>> 0x0000000040000000-0x00000000ffffffff] on arm64.
>>>>>>
>>>>>>   From the above discussion, on your platform, the low crashkernel fall in
>>>>>> DMA32 region, but your environment needs to access DMA
>>>>>> region, so there is the call trace.
>>>>>>
>>>>>> I have a question, why do you choose 0xc0000000 here?
>>>>>>
>>>>>> Besides, this is common code, we also need to consider about x86.
>>>>>>
>>>>>    + nsaenzjulienne@...e.de
>>> Thanks for adding me to the conversation, and sorry for the headaches.
>>>
>>>>>     Exactly .  This is why it needs to be a CONFIG option for  Raspberry
>>>>> ..,  or device tree option.
>>>>>
>>>>>
>>>>>     We could revert 1a8e1cef7 since it broke  Arm kdump too.
>>>> Well, unfortunately the patch for commit 1a8e1cef7603 ("arm64: use
>>>> both ZONE_DMA and ZONE_DMA32") was not Cc'ed to the kexec mailing
>>>> list, thus we couldn't get many eyes on it for a thorough review from
>>>> kexec/kdump p-o-v.
>>>>
>>>> Also we historically never had distinction in common arch code on the
>>>> basis of the intended end use-case: embedded, server or automotive, so
>>>> I am not sure introducing a Raspberry specific CONFIG option would be
>>>> a good idea.
>>> +1
>>>
>>>   From the distros perspective it's very important to keep a single kernel image.
>>>
>>>> So, rather than reverting the patch, we can look at addressing the
>>>> same properly this time - especially from a kdump p-o-v.
>>>> This issue has been reported by some Red Hat arm64 partners with
>>>> upstream kernel also and as we have noticed in the past as well,
>>>> hardcoding the placement of the crashkernel base address (unless the
>>>> base address is specified by a crashkernel=X@Y like bootargs) is also
>>>> not a portable suggestion.
>>>>
>>>> I am working on a possible fix and will have more updates on the same
>>>> in a day-or-two.
>>> Please keep me in the loop, we've also had issues pointing to this reported by
>>> SUSE partners. I can do some testing both on the RPi4 and on big servers that
>>> need huge crashkernel sizes.
>>>
>>> Regards,
>>> Nicolas
>>>
>>    Hi
>>
>>    Has there been any progress on this ? It appears we are stalled because Nicolas's  and Chen's changes are not compatible . One is needed for RPi4 and the other for server class equipment.
>>
>>
>> Thanks,
>>
>> John
>>
>>
> Hi all,
>
> Thanks for John's reminder.
> commit 1a8e1cef7 ("arm64: use both ZONE_DMA and ZONE_DMA32") broken the arm64 kdump,
> there is a simple solution similar to pk's to fix this, see below:
>
> In crash dump kernel, if the peripherals need to use ZONE_DMA like the the Raspberry Pi 4, based on
> my solution, we adjusted the memory range in memblock_find_in_range.
>
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index a7580d291c37..eb16c6d54b73 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -320,6 +320,7 @@ int __init reserve_crashkernel_low(void)
>          unsigned long long base, low_base = 0, low_size = 0;
>          unsigned long total_low_mem;
>          int ret;
> +       phys_addr_t crash_max = 1ULL << 32;
>   
>          total_low_mem = memblock_mem_size(1UL << (32 - PAGE_SHIFT));
>   
> @@ -352,7 +353,12 @@ int __init reserve_crashkernel_low(void)
>                          return 0;
>          }
>   
> -       low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
> +#ifdef CONFIG_ARM64
> +       if (IS_ENABLED(CONFIG_ZONE_DMA)) {
> +               crash_max = arm64_dma_phys_limit;
> +       }
> +#endif
> +       low_base = memblock_find_in_range(0, crash_max, low_size, CRASH_ALIGN);
>          if (!low_base) {
>                  pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
>                         (unsigned long)(low_size >> 20));
>
>
> Thanks,
> Chen Zhou
>
Hi,

I don't have any objections to this proposal.






>> .
>>
>

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