From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: From: Chen Zhou Subject: [PATCH v11 5/5] kdump: update Documentation about crashkernel Date: Sat, 1 Aug 2020 21:08:56 +0800 Message-ID: <20200801130856.86625-6-chenzhou10@huawei.com> In-Reply-To: <20200801130856.86625-1-chenzhou10@huawei.com> References: <20200801130856.86625-1-chenzhou10@huawei.com> MIME-Version: 1.0 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: catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, tglx@linutronix.de, mingo@redhat.com, dyoung@redhat.com, bhe@redhat.com, corbet@lwn.net, John.P.donnelly@oracle.com, prabhakar.pkin@gmail.com, bhsharma@redhat.com Cc: wangkefeng.wang@huawei.com, arnd@arndb.de, linux-doc@vger.kernel.org, chenzhou10@huawei.com, xiexiuqi@huawei.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, robh+dt@kernel.org, horms@verge.net.au, nsaenzjulienne@suse.de, huawei.libin@huawei.com, guohanjun@huawei.com, linux-arm-kernel@lists.infradead.org Now the behavior of crashkernel=X has been changed, which 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 well. So add a threshold and go for high allocation directly if the required size is too large. The threshold is set as the half of 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. For non-RPi4 platforms, change ZONE_DMA memtioned above to ZONE_DMA32. So update the Documentation. Signed-off-by: Chen Zhou --- Documentation/admin-guide/kdump/kdump.rst | 21 ++++++++++++++++--- .../admin-guide/kernel-parameters.txt | 11 ++++++++-- 2 files changed, 27 insertions(+), 5 deletions(-) diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst index 2da65fef2a1c..4b58f97351d5 100644 --- a/Documentation/admin-guide/kdump/kdump.rst +++ b/Documentation/admin-guide/kdump/kdump.rst @@ -299,7 +299,15 @@ Boot into System Kernel "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory starting at physical address 0x01000000 (16MB) for the dump-capture kernel. - On x86 and x86_64, use "crashkernel=64M@16M". + On x86 use "crashkernel=64M@16M". + + On x86_64, use "crashkernel=X" to select a region under 4G first, and + fall back to reserve region above 4G. + We can also use "crashkernel=X,high" to select a region above 4G, which + also tries to allocate at least 256M below 4G automatically and + "crashkernel=Y,low" can be used to allocate specified size low memory. + Use "crashkernel=Y@X" if you really have to reserve memory from specified + start address X. On ppc64, use "crashkernel=128M@32M". @@ -316,8 +324,15 @@ Boot into System Kernel kernel will automatically locate the crash kernel image within the first 512MB of RAM if X is not given. - On arm64, use "crashkernel=Y[@X]". Note that the start address of - the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000). + On arm64, use "crashkernel=X" to try low allocation in ZONE_DMA, and + fall back to high allocation if it fails. And go for high allocation + directly if the required size is too large. 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. + For non-RPi4 platforms, change ZONE_DMA memtioned above to ZONE_DMA32. + Use "crashkernel=Y@X" if you really have to reserve memory from + specified start address X. Note that the start address of the kernel, + X if explicitly specified, must be aligned to 2MiB (0x200000). Load the Dump-capture Kernel ============================ diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index fb95fad81c79..d1b6016850d6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -722,6 +722,10 @@ [KNL, x86_64] select a region under 4G first, and fall back to reserve region above 4G when '@offset' hasn't been specified. + [KNL, arm64] Try low allocation in ZONE_DMA, fall back + to high allocation if it fails when '@offset' hasn't been + specified. For non-RPi4 platforms, change ZONE_DMA to + ZONE_DMA32. See Documentation/admin-guide/kdump/kdump.rst for further details. crashkernel=range1:size1[,range2:size2,...][@offset] @@ -746,13 +750,16 @@ 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. Kernel would try to allocate at - at least 256M below 4G automatically. + least 256M below 4G automatically. This one let user to specify own low range under 4G for second kernel instead. 0: to disable low allocation. It will be ignored when crashkernel=X,high is not used or memory reserved is below 4G. - + [KNL, arm64] range under 4G. + This one let user to specify a low range in ZONE_DMA for + crash dump kernel. For non-RPi4 platforms, change ZONE_DMA + to ZONE_DMA32. cryptomgr.notests [KNL] Disable crypto self-tests -- 2.20.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec