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 431B1C7EE23 for ; Sun, 4 Jun 2023 03:51:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229714AbjFDDvv (ORCPT ); Sat, 3 Jun 2023 23:51:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50164 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229588AbjFDDvq (ORCPT ); Sat, 3 Jun 2023 23:51:46 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6B303E1 for ; Sat, 3 Jun 2023 20:50:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685850657; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; 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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230511085139.1039088-2-chenjiahao16@huawei.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Jiahao, On 05/11/23 at 04:51pm, Chen Jiahao wrote: ...... > @@ -1300,14 +1325,34 @@ static void __init reserve_crashkernel(void) > return; > } > > - ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(), > + ret = parse_crashkernel(cmdline, memblock_phys_mem_size(), > &crash_size, &crash_base); > - if (ret || !crash_size) > + if (ret == -ENOENT) { > + /* Fallback to crashkernel=X,[high,low] */ > + ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base); > + if (ret || !crash_size) > + return; > + > + /* > + * crashkernel=Y,low is valid only when crashkernel=X,high > + * is passed. > + */ > + ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base); > + if (ret == -ENOENT) > + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; > + else if (ret) > + return; > + > + search_end = memblock_end_of_DRAM(); > + } else if (ret || !crash_size) { > + /* Invalid argument value specified */ > return; > + } The parsing part looks great, while you didn't mark if it's specified high reservation, please see later comment why it's needed. > > crash_size = PAGE_ALIGN(crash_size); > > if (crash_base) { > + fixed_base = true; > search_start = crash_base; > search_end = crash_base + crash_size; > } > @@ -1320,17 +1365,31 @@ static void __init reserve_crashkernel(void) > * swiotlb can work on the crash kernel. > */ > crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE, > - search_start, > - min(search_end, (unsigned long) SZ_4G)); > + search_start, search_end); If it's a specified high reservation, you have search_start = memblock_start_of_DRAM(); search_end = memblock_end_of_DRAM(); Then it attempts to search top down first time here. > if (crash_base == 0) { > - /* Try again without restricting region to 32bit addressible memory */ > + if (fixed_base) { > + pr_warn("crashkernel: allocating failed with given size@offset\n"); > + return; > + } > + search_end = memblock_end_of_DRAM(); > + > + /* Try again above the region of 32bit addressible memory */ > crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE, > - search_start, search_end); > + search_start, search_end); If crashkernel=,high case, the first attempt failed, here it assigns search_end with memblock_end_of_DRAM(). It's the exactly the same attempt, why is that needed? Why don't you use a local variable 'high' to mark the crashkernel=,hig, then judge when deciding how to adjsut the reservation range. Do I misunderstand the code? Thanks Baoquan > if (crash_base == 0) { > pr_warn("crashkernel: couldn't allocate %lldKB\n", > crash_size >> 10); > return; > } > + > + if (!crash_low_size) > + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; > + } > + > + if ((crash_base > dma32_phys_limit - crash_low_size) && > + crash_low_size && reserve_crashkernel_low(crash_low_size)) { > + memblock_phys_free(crash_base, crash_size); > + return; > } > > pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n", > -- > 2.31.1 >