From: Borislav Petkov <bp@alien8.de>
To: Baoquan He <bhe@redhat.com>
Cc: 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,
Catalin Marinas <catalin.marinas@arm.com>,
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 03/10] x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions reserve_crashkernel()
Date: Thu, 16 Dec 2021 11:55:55 +0100 [thread overview]
Message-ID: <YbsbO1XnrzLAIBEu@zn.tnic> (raw)
In-Reply-To: <20211216011040.GG3023@MiWiFi-R3L-srv>
On Thu, Dec 16, 2021 at 09:10:40AM +0800, Baoquan He wrote:
> reserve_crashkernel_low() always return 0 on x86_32, so the not equivalent
> transformation for x86_32 doesn't matter, I think.
That is, of course, very obvious... not!
Why is that function parsing crashkernel=XM, and crashkernel=X,high,
then it attempts some low memory reservation too? Why isn't
crashkernel=Y,low parsed there too?
I guess this alludes to why:
crashkernel=size[KMG],low
[KNL, X86-64] range under 4G. When crashkernel=X,high
is passed, kernel could allocate physical memory region
above 4G, that cause second kernel crash on system
that require some amount of low memory, e.g. swiotlb
requires at least 64M+32K low memory, also enough extra
low memory is needed to make sure DMA buffers for 32-bit
devices won't run out.
So, before this is going anywhere, I'd like to see this function
documented properly. I see Documentation/admin-guide/kdump/kdump.rst
explains the crashkernel= options too so you can refer to it in the
comments so that when someone looks at that code, someone can follow why
it is doing what it is doing.
Then, as a future work, all that parsing of crashkernel= cmdline options
should be concentrated at the beginning and once it is clear what the
user requests, the reservations should be done.
As it is, reserve_crashkernel() is pretty unwieldy and hard to read.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
WARNING: multiple messages have this Message-ID (diff)
From: Borislav Petkov <bp@alien8.de>
To: Baoquan He <bhe@redhat.com>
Cc: 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,
Catalin Marinas <catalin.marinas@arm.com>,
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 03/10] x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions reserve_crashkernel()
Date: Thu, 16 Dec 2021 11:55:55 +0100 [thread overview]
Message-ID: <YbsbO1XnrzLAIBEu@zn.tnic> (raw)
In-Reply-To: <20211216011040.GG3023@MiWiFi-R3L-srv>
On Thu, Dec 16, 2021 at 09:10:40AM +0800, Baoquan He wrote:
> reserve_crashkernel_low() always return 0 on x86_32, so the not equivalent
> transformation for x86_32 doesn't matter, I think.
That is, of course, very obvious... not!
Why is that function parsing crashkernel=XM, and crashkernel=X,high,
then it attempts some low memory reservation too? Why isn't
crashkernel=Y,low parsed there too?
I guess this alludes to why:
crashkernel=size[KMG],low
[KNL, X86-64] range under 4G. When crashkernel=X,high
is passed, kernel could allocate physical memory region
above 4G, that cause second kernel crash on system
that require some amount of low memory, e.g. swiotlb
requires at least 64M+32K low memory, also enough extra
low memory is needed to make sure DMA buffers for 32-bit
devices won't run out.
So, before this is going anywhere, I'd like to see this function
documented properly. I see Documentation/admin-guide/kdump/kdump.rst
explains the crashkernel= options too so you can refer to it in the
comments so that when someone looks at that code, someone can follow why
it is doing what it is doing.
Then, as a future work, all that parsing of crashkernel= cmdline options
should be concentrated at the beginning and once it is clear what the
user requests, the reservations should be done.
As it is, reserve_crashkernel() is pretty unwieldy and hard to read.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Borislav Petkov <bp@alien8.de>
To: Baoquan He <bhe@redhat.com>
Cc: 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,
Catalin Marinas <catalin.marinas@arm.com>,
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 03/10] x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions reserve_crashkernel()
Date: Thu, 16 Dec 2021 11:55:55 +0100 [thread overview]
Message-ID: <YbsbO1XnrzLAIBEu@zn.tnic> (raw)
In-Reply-To: <20211216011040.GG3023@MiWiFi-R3L-srv>
On Thu, Dec 16, 2021 at 09:10:40AM +0800, Baoquan He wrote:
> reserve_crashkernel_low() always return 0 on x86_32, so the not equivalent
> transformation for x86_32 doesn't matter, I think.
That is, of course, very obvious... not!
Why is that function parsing crashkernel=XM, and crashkernel=X,high,
then it attempts some low memory reservation too? Why isn't
crashkernel=Y,low parsed there too?
I guess this alludes to why:
crashkernel=size[KMG],low
[KNL, X86-64] range under 4G. When crashkernel=X,high
is passed, kernel could allocate physical memory region
above 4G, that cause second kernel crash on system
that require some amount of low memory, e.g. swiotlb
requires at least 64M+32K low memory, also enough extra
low memory is needed to make sure DMA buffers for 32-bit
devices won't run out.
So, before this is going anywhere, I'd like to see this function
documented properly. I see Documentation/admin-guide/kdump/kdump.rst
explains the crashkernel= options too so you can refer to it in the
comments so that when someone looks at that code, someone can follow why
it is doing what it is doing.
Then, as a future work, all that parsing of crashkernel= cmdline options
should be concentrated at the beginning and once it is clear what the
user requests, the reservations should be done.
As it is, reserve_crashkernel() is pretty unwieldy and hard to read.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
next prev parent reply other threads:[~2021-12-16 10:56 UTC|newest]
Thread overview: 198+ 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 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` [PATCH v17 01/10] x86: kdump: replace the hard-coded alignment with macro CRASH_ALIGN Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 13:17 ` Baoquan He
2021-12-13 13:17 ` Baoquan He
2021-12-13 13:17 ` Baoquan He
2021-12-14 8:41 ` Leizhen (ThunderTown)
2021-12-14 8:41 ` Leizhen (ThunderTown)
2021-12-14 8:41 ` Leizhen (ThunderTown)
2021-12-13 14:26 ` john.p.donnelly
2021-12-13 14:26 ` john.p.donnelly
2021-12-13 14:26 ` john.p.donnelly
2021-12-13 19:54 ` Borislav Petkov
2021-12-13 19:54 ` Borislav Petkov
2021-12-13 19:54 ` Borislav Petkov
2021-12-14 9:27 ` Leizhen (ThunderTown)
2021-12-14 9:27 ` Leizhen (ThunderTown)
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
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 13:37 ` Baoquan He
2021-12-13 13:37 ` Baoquan He
2021-12-13 13:37 ` Baoquan He
2021-12-14 8:48 ` Leizhen (ThunderTown)
2021-12-14 8:48 ` Leizhen (ThunderTown)
2021-12-14 8:48 ` Leizhen (ThunderTown)
2021-12-13 14:27 ` john.p.donnelly
2021-12-13 14:27 ` john.p.donnelly
2021-12-13 14:27 ` john.p.donnelly
2021-12-14 19:07 ` Borislav Petkov
2021-12-14 19:07 ` Borislav Petkov
2021-12-14 19:07 ` Borislav Petkov
2021-12-14 19:24 ` Catalin Marinas
2021-12-14 19:24 ` Catalin Marinas
2021-12-14 19:24 ` Catalin Marinas
2021-12-15 2:10 ` Leizhen (ThunderTown)
2021-12-15 2:10 ` Leizhen (ThunderTown)
2021-12-15 2:10 ` Leizhen (ThunderTown)
2021-12-15 3:42 ` Baoquan He
2021-12-15 3:42 ` Baoquan He
2021-12-15 3:42 ` Baoquan He
2021-12-15 11:01 ` Catalin Marinas
2021-12-15 11:01 ` Catalin Marinas
2021-12-15 11:01 ` Catalin Marinas
2021-12-15 11:16 ` Baoquan He
2021-12-15 11:16 ` Baoquan He
2021-12-15 11:16 ` Baoquan He
2021-12-15 11:45 ` Leizhen (ThunderTown)
2021-12-15 11:45 ` Leizhen (ThunderTown)
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
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 14:28 ` john.p.donnelly
2021-12-13 14:28 ` john.p.donnelly
2021-12-13 14:28 ` john.p.donnelly
2021-12-14 8:54 ` Baoquan He
2021-12-14 8:54 ` Baoquan He
2021-12-14 8:54 ` Baoquan He
2021-12-14 9:38 ` Borislav Petkov
2021-12-14 9:38 ` Borislav Petkov
2021-12-14 9:38 ` Borislav Petkov
2021-12-14 9:56 ` Baoquan He
2021-12-14 9:56 ` Baoquan He
2021-12-14 9:56 ` Baoquan He
2021-12-14 14:24 ` Borislav Petkov
2021-12-14 14:24 ` Borislav Petkov
2021-12-14 14:24 ` Borislav Petkov
2021-12-15 6:01 ` Baoquan He
2021-12-15 6:01 ` Baoquan He
2021-12-15 6:01 ` Baoquan He
2021-12-15 13:28 ` Borislav Petkov
2021-12-15 13:28 ` Borislav Petkov
2021-12-15 13:28 ` Borislav Petkov
2021-12-16 1:10 ` Baoquan He
2021-12-16 1:10 ` Baoquan He
2021-12-16 1:10 ` Baoquan He
2021-12-16 2:46 ` Leizhen (ThunderTown)
2021-12-16 2:46 ` Leizhen (ThunderTown)
2021-12-16 2:46 ` Leizhen (ThunderTown)
2021-12-16 11:07 ` Borislav Petkov
2021-12-16 11:07 ` Borislav Petkov
2021-12-16 11:07 ` Borislav Petkov
2021-12-16 12:08 ` Leizhen (ThunderTown)
2021-12-16 12:08 ` Leizhen (ThunderTown)
2021-12-16 12:08 ` Leizhen (ThunderTown)
2021-12-16 12:23 ` Leizhen (ThunderTown)
2021-12-16 12:23 ` Leizhen (ThunderTown)
2021-12-16 12:23 ` Leizhen (ThunderTown)
2021-12-16 14:48 ` Borislav Petkov
2021-12-16 14:48 ` Borislav Petkov
2021-12-16 14:48 ` Borislav Petkov
2021-12-17 2:51 ` Leizhen (ThunderTown)
2021-12-17 2:51 ` Leizhen (ThunderTown)
2021-12-17 2:51 ` Leizhen (ThunderTown)
2021-12-21 22:23 ` Borislav Petkov
2021-12-21 22:23 ` Borislav Petkov
2021-12-21 22:23 ` Borislav Petkov
2021-12-16 10:55 ` Borislav Petkov [this message]
2021-12-16 10:55 ` Borislav Petkov
2021-12-16 10:55 ` Borislav Petkov
2021-12-16 14:11 ` Baoquan He
2021-12-16 14:11 ` Baoquan He
2021-12-16 14:11 ` Baoquan He
2021-12-16 14:58 ` Borislav Petkov
2021-12-16 14:58 ` Borislav Petkov
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
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 14:29 ` john.p.donnelly
2021-12-13 14:29 ` john.p.donnelly
2021-12-13 14:29 ` john.p.donnelly
2021-12-14 11:40 ` Leizhen (ThunderTown)
2021-12-14 11:40 ` Leizhen (ThunderTown)
2021-12-14 11:40 ` Leizhen (ThunderTown)
2021-12-15 8:56 ` Leizhen (ThunderTown)
2021-12-15 8:56 ` Leizhen (ThunderTown)
2021-12-15 8:56 ` Leizhen (ThunderTown)
2021-12-15 9:22 ` Baoquan He
2021-12-15 9:22 ` Baoquan He
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
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 14:30 ` john.p.donnelly
2021-12-13 14:30 ` john.p.donnelly
2021-12-13 14:30 ` john.p.donnelly
2021-12-14 10:45 ` Baoquan He
2021-12-14 10:45 ` Baoquan He
2021-12-14 10:45 ` Baoquan He
2021-12-14 12:38 ` Leizhen (ThunderTown)
2021-12-14 12:38 ` Leizhen (ThunderTown)
2021-12-14 12:38 ` Leizhen (ThunderTown)
2021-12-16 11:17 ` Borislav Petkov
2021-12-16 11:17 ` Borislav Petkov
2021-12-16 11:17 ` Borislav Petkov
2021-12-16 13:15 ` Leizhen (ThunderTown)
2021-12-16 13:15 ` Leizhen (ThunderTown)
2021-12-16 13:15 ` Leizhen (ThunderTown)
2021-12-16 14:51 ` Borislav Petkov
2021-12-16 14:51 ` Borislav Petkov
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
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 14:30 ` john.p.donnelly
2021-12-13 14:30 ` john.p.donnelly
2021-12-13 14:30 ` john.p.donnelly
2021-12-10 6:55 ` [PATCH v17 07/10] arm64: kdump: reimplement crashkernel=X Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 14:31 ` john.p.donnelly
2021-12-13 14:31 ` john.p.donnelly
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 6:55 ` [PATCH v17 08/10] of: fdt: Aggregate the processing of "linux, usable-memory-range" Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-10 16:39 ` [PATCH v17 08/10] of: fdt: Aggregate the processing of "linux,usable-memory-range" Rob Herring
2021-12-10 16:39 ` Rob Herring
2021-12-10 16:39 ` Rob Herring
2021-12-13 14:34 ` john.p.donnelly
2021-12-13 14:34 ` john.p.donnelly
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 6:55 ` [PATCH v17 09/10] of: fdt: Add memory for devices by DT property "linux, usable-memory-range" Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-10 16:43 ` [PATCH v17 09/10] of: fdt: Add memory for devices by DT property "linux,usable-memory-range" Rob Herring
2021-12-10 16:43 ` Rob Herring
2021-12-10 16:43 ` Rob Herring
2021-12-13 14:33 ` john.p.donnelly
2021-12-13 14:33 ` john.p.donnelly
2021-12-13 14:33 ` john.p.donnelly
2021-12-10 6:55 ` [PATCH v17 10/10] kdump: update Documentation about crashkernel Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-10 6:55 ` Zhen Lei
2021-12-13 14:34 ` john.p.donnelly
2021-12-13 14:34 ` john.p.donnelly
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
2021-12-10 7:15 ` Kefeng Wang
2021-12-10 7:15 ` Kefeng Wang
2021-12-13 18:50 ` Will Deacon
2021-12-13 18:50 ` Will Deacon
2021-12-13 18:50 ` Will Deacon
2021-12-13 14:37 ` john.p.donnelly
2021-12-13 14:37 ` john.p.donnelly
2021-12-13 14:37 ` john.p.donnelly
2021-12-13 18:56 ` Catalin Marinas
2021-12-13 18:56 ` Catalin Marinas
2021-12-13 18:56 ` Catalin Marinas
2021-12-13 18:57 ` Borislav Petkov
2021-12-13 18:57 ` Borislav Petkov
2021-12-13 18:57 ` Borislav Petkov
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