From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2E9CC433F5 for ; Thu, 5 May 2022 17:02:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230131AbiEERFk (ORCPT ); Thu, 5 May 2022 13:05:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50510 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1382496AbiEERFb (ORCPT ); Thu, 5 May 2022 13:05:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B4E05C840; Thu, 5 May 2022 10:01:32 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 98ED961E8A; Thu, 5 May 2022 17:01:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8A37C385A4; Thu, 5 May 2022 17:01:26 +0000 (UTC) Date: Thu, 5 May 2022 18:01:23 +0100 From: Catalin Marinas To: Zhen Lei Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , linux-kernel@vger.kernel.org, Dave Young , Baoquan He , Vivek Goyal , Eric Biederman , kexec@lists.infradead.org, Will Deacon , linux-arm-kernel@lists.infradead.org, Rob Herring , Frank Rowand , devicetree@vger.kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org, Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , John Donnelly , Dave Kleikamp Subject: Re: [PATCH v23 3/6] arm64: kdump: Reimplement crashkernel=X Message-ID: References: <20220505091845.167-1-thunder.leizhen@huawei.com> <20220505091845.167-4-thunder.leizhen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220505091845.167-4-thunder.leizhen@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, May 05, 2022 at 05:18:42PM +0800, Zhen Lei wrote: > From: Chen Zhou > > There are following issues in arm64 kdump: > 1. We use crashkernel=X to reserve crashkernel in DMA zone, which > will fail when there is not enough low memory. > 2. If reserving crashkernel above DMA zone, in this case, crash dump > kernel will fail to boot because there is no low memory available > for allocation. > > To solve these issues, introduce crashkernel=X,[high,low]. > The "crashkernel=X,high" is used to select a region above DMA zone, and > the "crashkernel=Y,low" is used to allocate specified size low memory. Thanks for posting the simplified version, though the discussion with Baoquan is still ongoing. AFAICT there is no fallback if crashkernel= fails. The advantage with this series is cleaner code, we set the limits during parsing and don't have to adjust them if some of the first allocation failed. > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 51863f1448c6989..11406f3e1443168 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -90,6 +90,32 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit; > phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; > #endif > > +/* Current arm64 boot protocol requires 2MB alignment */ > +#define CRASH_ALIGN SZ_2M > + > +#define CRASH_ADDR_LOW_MAX arm64_dma_phys_limit > +#define CRASH_ADDR_HIGH_MAX memblock.current_limit Better use memblock_get_current_limit() if you need to or just MEMBLOCK_ALLOC_ANYWHERE, memblock.current_limit is just a memblock internal. But I think we can go for (PHYS_MASK + 1) if you need something other than MEMBLOCK_ALLOC_ANYWHERE, memblock knows what to allocate anyway. > +static int __init reserve_crashkernel_low(unsigned long long low_size) > +{ > + unsigned long long low_base; > + > + low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX); > + if (!low_base) { > + pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size); > + return -ENOMEM; > + } > + > + pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n", > + low_base, low_base + low_size, low_size >> 20); > + > + crashk_low_res.start = low_base; > + crashk_low_res.end = low_base + low_size - 1; > + insert_resource(&iomem_resource, &crashk_low_res); > + > + return 0; > +} > + > /* > * reserve_crashkernel() - reserves memory for crash kernel > * > @@ -100,17 +126,32 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; > static void __init reserve_crashkernel(void) > { > unsigned long long crash_base, crash_size; > - unsigned long long crash_max = arm64_dma_phys_limit; > + unsigned long long crash_low_size = 0; > + unsigned long long crash_max = CRASH_ADDR_LOW_MAX; > + char *cmdline = boot_command_line; > int ret; > > if (!IS_ENABLED(CONFIG_KEXEC_CORE)) > return; > > - ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(), > + /* crashkernel=X[@offset] */ > + ret = parse_crashkernel(cmdline, memblock_phys_mem_size(), > &crash_size, &crash_base); > - /* no crashkernel= or invalid value specified */ > - if (ret || !crash_size) > - return; > + if (ret || !crash_size) { I think we should check for ret == -ENOENT only. If the crashkernel= exists but is malformed or the size is 0, we shouldn't bother with high/low at all. > + ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base); > + if (ret || !crash_size) > + return; > + > + /* > + * crashkernel=Y,low can be specified or not, but invalid value > + * is not allowed. > + */ > + ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base); > + if (ret && (ret != -ENOENT)) > + return; > + > + crash_max = CRASH_ADDR_HIGH_MAX; > + } > > crash_size = PAGE_ALIGN(crash_size); > > @@ -118,8 +159,7 @@ static void __init reserve_crashkernel(void) > if (crash_base) > crash_max = crash_base + crash_size; > > - /* Current arm64 boot protocol requires 2MB alignment */ > - crash_base = memblock_phys_alloc_range(crash_size, SZ_2M, > + crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, > crash_base, crash_max); > if (!crash_base) { > pr_warn("cannot allocate crashkernel (size:0x%llx)\n", I personally like this but let's see how the other thread goes. I guess if we want a fallback, it would come just before the check the above: if (!crash_base && crash_max != CRASH_ADDR_HIGH_MAX) { /* attempt high allocation with default low */ if (!crash_low_size) crash_low_size = some default; crash_max = CRASH_ADDR_LOW_MAX; crash_base = memblock_phys_alloc_range(); } Well, I guess we end up with your earlier proposal but I think I understand it better now ;). -- Catalin