From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Date: Tue, 1 Sep 2020 18:13:07 +0100 From: Catalin Marinas Subject: Re: [PATCH v11 5/5] kdump: update Documentation about crashkernel Message-ID: <20200901171306.GK5561@gaia> References: <20200801130856.86625-1-chenzhou10@huawei.com> <20200801130856.86625-6-chenzhou10@huawei.com> <20200808100239.GB60590@dhcp-128-65.nay.redhat.com> <96d0da23-d484-7f66-1680-07b4b5984831@huawei.com> <20200810060355.GB6988@dhcp-128-65.nay.redhat.com> <2e6aebf9-3765-5d8c-933c-698442db1d52@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2e6aebf9-3765-5d8c-933c-698442db1d52@huawei.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: chenzhou 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, Dave Young , 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 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 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec