From: Catalin Marinas <catalin.marinas@arm.com>
To: chenzhou <chenzhou10@huawei.com>
Cc: Dave Young <dyoung@redhat.com>,
will@kernel.org, james.morse@arm.com, tglx@linutronix.de,
mingo@redhat.com, bhe@redhat.com, corbet@lwn.net,
John.P.donnelly@oracle.com, prabhakar.pkin@gmail.com,
bhsharma@redhat.com, horms@verge.net.au, robh+dt@kernel.org,
arnd@arndb.de, nsaenzjulienne@suse.de,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
linux-doc@vger.kernel.org, guohanjun@huawei.com,
xiexiuqi@huawei.com, huawei.libin@huawei.com,
wangkefeng.wang@huawei.com
Subject: Re: [PATCH v11 5/5] kdump: update Documentation about crashkernel
Date: Tue, 1 Sep 2020 18:13:07 +0100 [thread overview]
Message-ID: <20200901171306.GK5561@gaia> (raw)
In-Reply-To: <2e6aebf9-3765-5d8c-933c-698442db1d52@huawei.com>
On Tue, Aug 18, 2020 at 03:07:04PM +0800, chenzhou wrote:
> On 2020/8/10 14:03, Dave Young wrote:
> >>> Previously I remember we talked about to use similar logic as X86, but I
> >>> remember you mentioned on some arm64 platform there could be no low
> >>> memory at all. Is this not a problem now for the fallback? Just be
> >>> curious, thanks for the update, for the common part looks good.
> >>
> >> Did you mean this discuss: https://lkml.org/lkml/2019/12/27/122?
> > I meant about this reply instead :)
> > https://lkml.org/lkml/2020/1/16/616
>
> Sorry for not repley in time, I was on holiday last week.
>
> The platform James mentioned may exist for which have no devices and
> need no low memory.
If there is no memory below 4GB, the arm64 kernel assumes that the
32-bit devices will have some DMA offsets shifting the addresses to the
bottom of the available RAM. So even if RAM starts above 4GB, we
ZONE_DMA32 will be allocated in the bottom 4GB of the high memory (and
if the hardware designers forgot to shift those DMA accesses, we don't
have to support the platform ;)).
So the arm64 notion of low memory differs slightly from the x86 one.
--
Catalin
next prev parent reply other threads:[~2020-09-01 17:13 UTC|newest]
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
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 [this message]
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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