From: Baoquan He <bhe@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Borislav Petkov <bp@alien8.de>,
Zhen Lei <thunder.leizhen@huawei.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, Dave Young <dyoung@redhat.com>,
Vivek Goyal <vgoyal@redhat.com>,
Eric Biederman <ebiederm@xmission.com>,
kexec@lists.infradead.org, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
devicetree@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
linux-doc@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
Feng Zhou <zhoufeng.zf@bytedance.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Chen Zhou <dingguo.cz@antgroup.com>
Subject: Re: [PATCH v17 02/10] x86: kdump: make the lower bound of crash kernel reservation consistent
Date: Wed, 15 Dec 2021 19:16:43 +0800 [thread overview]
Message-ID: <20211215111643.GF3023@MiWiFi-R3L-srv> (raw)
In-Reply-To: <YbnK79c0YokJ1ahu@arm.com>
On 12/15/21 at 11:01am, Catalin Marinas wrote:
> On Wed, Dec 15, 2021 at 11:42:19AM +0800, Baoquan He wrote:
> > On 12/14/21 at 07:24pm, Catalin Marinas wrote:
> > > On Tue, Dec 14, 2021 at 08:07:58PM +0100, Borislav Petkov wrote:
> > > > On Fri, Dec 10, 2021 at 02:55:25PM +0800, Zhen Lei wrote:
> > > > > From: Chen Zhou <chenzhou10@huawei.com>
> > > > >
> > > > > The lower bounds of crash kernel reservation and crash kernel low
> > > > > reservation are different, use the consistent value CRASH_ALIGN.
> > > >
> > > > A big WHY is missing here to explain why the lower bound of the
> > > > allocation range needs to be 16M and why was 0 wrong?
> > >
> > > I asked the same here:
> > >
> > > https://lore.kernel.org/r/20210224143547.GB28965@arm.com
> > >
> > > IIRC Baoquan said that there is a 1MB reserved for x86 anyway in the
> > > lower part, so that's equivalent in practice to starting from
> > > CRASH_ALIGN.
> >
> > Yeah, even for i386, there's area reserved by BIOS inside low 1M.
> > Considering the existing alignment CRASH_ALIGN which is 16M, we
> > definitely have no chance to get memory starting from 0. So starting
> > from 16M can skip the useless memblock searching, and make the
> > crashkernel low reservation consisten with crashkernel reservation on
> > allocation code.
>
> That's the x86 assumption. Is it valid for other architectures once the
> code has been made generic in patch 6? It should be ok for arm64, RAM
> tends to start from higher up but other architectures may start using
> this common code.
Good point. I didn't think of this from generic code side, then let's
keep it as 0.
>
> If you want to keep the same semantics as before, just leave it as 0.
> It's not that the additional lower bound makes the search slower.
Agree.
next prev parent reply other threads:[~2021-12-15 11:17 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-10 6:55 [PATCH v17 00/10] support reserving crashkernel above 4G on arm64 kdump Zhen Lei
2021-12-10 6:55 ` [PATCH v17 01/10] x86: kdump: replace the hard-coded alignment with macro CRASH_ALIGN Zhen Lei
2021-12-13 13:17 ` Baoquan He
2021-12-14 8:41 ` Leizhen (ThunderTown)
2021-12-13 14:26 ` john.p.donnelly
2021-12-13 19:54 ` Borislav Petkov
2021-12-14 9:27 ` Leizhen (ThunderTown)
2021-12-10 6:55 ` [PATCH v17 02/10] x86: kdump: make the lower bound of crash kernel reservation consistent Zhen Lei
2021-12-13 13:37 ` Baoquan He
2021-12-14 8:48 ` Leizhen (ThunderTown)
2021-12-13 14:27 ` john.p.donnelly
2021-12-14 19:07 ` Borislav Petkov
2021-12-14 19:24 ` Catalin Marinas
2021-12-15 2:10 ` Leizhen (ThunderTown)
2021-12-15 3:42 ` Baoquan He
2021-12-15 11:01 ` Catalin Marinas
2021-12-15 11:16 ` Baoquan He [this message]
2021-12-15 11:45 ` Leizhen (ThunderTown)
2021-12-10 6:55 ` [PATCH v17 03/10] x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions reserve_crashkernel() Zhen Lei
2021-12-13 14:28 ` john.p.donnelly
2021-12-14 8:54 ` Baoquan He
2021-12-14 9:38 ` Borislav Petkov
2021-12-14 9:56 ` Baoquan He
2021-12-14 14:24 ` Borislav Petkov
2021-12-15 6:01 ` Baoquan He
2021-12-15 13:28 ` Borislav Petkov
2021-12-16 1:10 ` Baoquan He
2021-12-16 2:46 ` Leizhen (ThunderTown)
2021-12-16 11:07 ` Borislav Petkov
2021-12-16 12:08 ` Leizhen (ThunderTown)
2021-12-16 12:23 ` Leizhen (ThunderTown)
2021-12-16 14:48 ` Borislav Petkov
2021-12-17 2:51 ` Leizhen (ThunderTown)
2021-12-21 22:23 ` Borislav Petkov
2021-12-16 10:55 ` Borislav Petkov
2021-12-16 14:11 ` Baoquan He
2021-12-16 14:58 ` Borislav Petkov
2021-12-10 6:55 ` [PATCH v17 04/10] x86: kdump: move xen_pv_domain() check and insert_resource() to setup_arch() Zhen Lei
2021-12-13 14:29 ` john.p.donnelly
2021-12-14 11:40 ` Leizhen (ThunderTown)
2021-12-15 8:56 ` Leizhen (ThunderTown)
2021-12-15 9:22 ` Baoquan He
2021-12-10 6:55 ` [PATCH v17 05/10] x86: kdump: move reserve_crashkernel[_low]() into crash_core.c Zhen Lei
2021-12-13 14:30 ` john.p.donnelly
2021-12-14 10:45 ` Baoquan He
2021-12-14 12:38 ` Leizhen (ThunderTown)
2021-12-16 11:17 ` Borislav Petkov
2021-12-16 13:15 ` Leizhen (ThunderTown)
2021-12-16 14:51 ` Borislav Petkov
2021-12-10 6:55 ` [PATCH v17 06/10] arm64: kdump: introduce some macros for crash kernel reservation Zhen Lei
2021-12-13 14:30 ` john.p.donnelly
2021-12-10 6:55 ` [PATCH v17 07/10] arm64: kdump: reimplement crashkernel=X Zhen Lei
2021-12-13 14:31 ` john.p.donnelly
2021-12-10 6:55 ` [PATCH v17 08/10] of: fdt: Aggregate the processing of "linux,usable-memory-range" Zhen Lei
2021-12-10 16:39 ` Rob Herring
2021-12-13 14:34 ` john.p.donnelly
2021-12-10 6:55 ` [PATCH v17 09/10] of: fdt: Add memory for devices by DT property "linux,usable-memory-range" Zhen Lei
2021-12-10 16:43 ` Rob Herring
2021-12-13 14:33 ` john.p.donnelly
2021-12-10 6:55 ` [PATCH v17 10/10] kdump: update Documentation about crashkernel Zhen Lei
2021-12-13 14:34 ` john.p.donnelly
2021-12-10 7:15 ` [PATCH v17 00/10] support reserving crashkernel above 4G on arm64 kdump Kefeng Wang
2021-12-13 18:50 ` Will Deacon
2021-12-13 14:37 ` john.p.donnelly
2021-12-13 18:56 ` Catalin Marinas
2021-12-13 18:57 ` Borislav Petkov
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