From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Subject: Re: [PATCH v11 3/5] arm64: kdump: reimplement crashkernel=X References: <20200801130856.86625-1-chenzhou10@huawei.com> <20200801130856.86625-4-chenzhou10@huawei.com> <20200902170910.GB16673@gaia> From: chenzhou Message-ID: Date: Thu, 3 Sep 2020 19:26:27 +0800 MIME-Version: 1.0 In-Reply-To: <20200902170910.GB16673@gaia> 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 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, dyoung@redhat.com, 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 Hi Catalin, On 2020/9/3 1:09, Catalin Marinas wrote: > On Sat, Aug 01, 2020 at 09:08:54PM +0800, Chen Zhou wrote: >> There are following issues in arm64 kdump: >> 1. We use crashkernel=X to reserve crashkernel below 4G, which >> will fail when there is no enough low memory. >> 2. If reserving crashkernel above 4G, in this case, crash dump >> kernel will boot failure because there is no low memory available >> for allocation. >> 3. Since commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32"), >> if the memory reserved for crash dump kernel falled in ZONE_DMA32, >> the devices in crash dump kernel need to use ZONE_DMA will alloc >> fail. >> >> To solve these issues, change the behavior of crashkernel=X. >> crashkernel=X 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 normally. >> So add a threshold and go for high allocation directly if the required >> size is too large. The value of threshold is set as the half of >> the 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. > Except for the threshold to keep zone ZONE_DMA memory, > reserve_crashkernel() looks very close to the x86 version. Shall we try > to make this generic as well? In the first instance, you could avoid the > threshold check if it takes an explicit ",high" option. Ok, i will try to do this. I look into the function reserve_crashkernel() of x86 and found the start address is CRASH_ALIGN in function memblock_find_in_range(), which is different with arm64. I don't figure out why is CRASH_ALIGN in x86, is there any specific reason? Thanks, Chen Zhou _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec