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From: chenzhou <chenzhou10@huawei.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: <wangkefeng.wang@huawei.com>, <linux-doc@vger.kernel.org>,
	<bhsharma@redhat.com>, <huawei.libin@huawei.com>,
	<guohanjun@huawei.com>, <will@kernel.org>, <bhe@redhat.com>,
	<corbet@lwn.net>, <mingo@redhat.com>, <dyoung@redhat.com>,
	<John.P.donnelly@oracle.com>, <arnd@arndb.de>,
	<xiexiuqi@huawei.com>, <horms@verge.net.au>, <tglx@linutronix.de>,
	<linux-arm-kernel@lists.infradead.org>,
	<kexec@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
	<robh+dt@kernel.org>, <james.morse@arm.com>,
	<prabhakar.pkin@gmail.com>, <nsaenzjulienne@suse.de>
Subject: Re: [PATCH v11 3/5] arm64: kdump: reimplement crashkernel=X
Date: Thu, 3 Sep 2020 21:18:51 +0800
Message-ID: <779fd86d-4d1a-c2ac-ffc8-79f05526a00c@huawei.com> (raw)
In-Reply-To: <f33a0ce6-552e-2f1a-e720-4f7124f15d1e@huawei.com>



On 2020/9/3 19:26, chenzhou wrote:
> Hi Catalin,
>
>
> On 2020/9/3 1:09, Catalin Marinas wrote:
>> On Sat, Aug 01, 2020 at 09:08:54PM +0800, Chen Zhou wrote:
>>> 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. If reserving crashkernel above 4G, in this case, crash dump
>>> kernel will boot failure because there is no low memory available
>>> for allocation.
>>> 3. Since commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32"),
>>> if the memory reserved for crash dump kernel falled in ZONE_DMA32,
>>> the devices in crash dump kernel need to use ZONE_DMA will alloc
>>> fail.
>>>
>>> To solve these issues, change the behavior of crashkernel=X.
>>> crashkernel=X tries low allocation in ZONE_DMA, and fall back to
>>> high allocation if it fails.
>>>
>>> If requized size X is too large and leads to very little free memory
>>> in ZONE_DMA after low allocation, the system may not work normally.
>>> So add a threshold and go for high allocation directly if the required
>>> size is too large. The value of threshold is set as the half of
>>> the low memory.
>>>
>>> If crash_base is outside ZONE_DMA, try to allocate at least 256M in
>>> ZONE_DMA automatically. "crashkernel=Y,low" can be used to allocate
>>> specified size low memory.
>> Except for the threshold to keep zone ZONE_DMA memory,
>> reserve_crashkernel() looks very close to the x86 version. Shall we try
>> to make this generic as well? In the first instance, you could avoid the
>> threshold check if it takes an explicit ",high" option.
> Ok, i will try to do this.
>
> I look into the function reserve_crashkernel() of x86 and found the start address is
> CRASH_ALIGN in function memblock_find_in_range(), which is different with arm64.
>
> I don't figure out why is CRASH_ALIGN in x86, is there any specific reason?
Besides, in function reserve_crashkernel_low() of x86, the start address is 0.

>
> Thanks,
> Chen Zhou
>
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
> .
>



  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 13:08 [PATCH v11 0/5] support reserving crashkernel above 4G on arm64 kdump Chen Zhou
2020-08-01 13:08 ` [PATCH v11 1/5] arm64: kdump: add macro CRASH_ALIGN and CRASH_ADDR_LOW_MAX Chen Zhou
2020-08-01 13:08 ` [PATCH v11 2/5] x86: kdump: move reserve_crashkernel_low() into crash_core.c Chen Zhou
2020-08-06 13:36   ` Ingo Molnar
2020-09-01 16:50     ` Catalin Marinas
2020-08-08  9:59   ` Dave Young
2020-08-01 13:08 ` [PATCH v11 3/5] arm64: kdump: reimplement crashkernel=X Chen Zhou
2020-09-02 17:09   ` Catalin Marinas
2020-09-03 11:26     ` chenzhou
2020-09-03 13:18       ` chenzhou [this message]
2020-09-04  3:04       ` Dave Young
2020-09-04  3:10         ` Dave Young
2020-09-04  4:02           ` chenzhou
2020-09-04  4:16             ` Dave Young
2020-09-04  6:39               ` chenzhou
2020-08-01 13:08 ` [PATCH v11 4/5] arm64: kdump: add memory for devices by DT property linux,usable-memory-range Chen Zhou
2020-08-01 13:08 ` [PATCH v11 5/5] kdump: update Documentation about crashkernel Chen Zhou
2020-08-08 10:02   ` Dave Young
2020-08-10  3:28     ` chenzhou
2020-08-10  5:59       ` Dave Young
2020-08-10  6:03       ` Dave Young
2020-08-18  7:07         ` chenzhou
2020-08-19 12:03           ` Dave Young
2020-08-28  1:59             ` chenzhou
2020-09-01 17:13           ` Catalin Marinas
2020-09-02 16:42           ` Catalin Marinas
2020-09-02 17:13   ` Catalin Marinas
2020-09-03 11:56     ` chenzhou
2020-08-06 11:37 ` [PATCH v11 0/5] support reserving crashkernel above 4G on arm64 kdump Dave Young

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