From patchwork Fri Apr 7 02:24:19 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baoquan He X-Patchwork-Id: 13204423 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D5B7EC761A6 for ; Fri, 7 Apr 2023 02:25:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=LlOwm9rtKkDk1UIE3rn8kCy9+zNDegvButFNG8Q5rI4=; b=K4DremMgiP+odJ +4K43ZBw2N5JYyXeFky4KpBzK6CSHHe27/8bA0+xPV8jbvcvKNF3NzxbfFEIXOZEycQztXl4ZwoQ3 yuXMlD+iCHtQziMGhVu/Lv4Bk4q+/dIvnE9lGfk14y8AXDlEvpieGMQ+U41tJvVfDMN5ZbHfPmkS7 7WknjoqP8jZAge1M4tDsvVs0yNoI2xGHdeJRQKBg4l6+zSiB4BhmTuWpisHPpyca+Ij1L/9wRaRro oUWL8AkeQ1XbP+wbc7TVM7LfIsXR5F2SE8upsxo78mE/+okxA1HN1oXVDwBVEzkdg80Hn42OV2YND iEd4eQKgh2E9TchwM7IA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pkbmK-0090xE-1W; Fri, 07 Apr 2023 02:24:40 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pkbmG-0090wL-31 for linux-arm-kernel@lists.infradead.org; Fri, 07 Apr 2023 02:24:38 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680834275; 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: content-transfer-encoding:content-transfer-encoding; bh=X3UzrBK11k5Mylgi6OpJengikN36MitOuwwGfpZwOEM=; b=ERBoYBYTNygr/wngzOKgr9fGbSOtAuJJ1oAjT77RWWt1m3urlLXihiYSx5AUrwmW7KrfTg 0EfZGnFrjMiUnwttDYLUWNoVdbaqqLMwSE8W3IP2nH4dbfc/SoAhzrvOMJ6BxUtkmR4plM 1DM+NFtrZkJD2RIGL7pvpUUr25r8fxg= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-269-Ka9gAEOsOFWGEx1xR6srcg-1; Thu, 06 Apr 2023 22:24:29 -0400 X-MC-Unique: Ka9gAEOsOFWGEx1xR6srcg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A085C3C01DFB; Fri, 7 Apr 2023 02:24:28 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-86.pek2.redhat.com [10.72.12.86]) by smtp.corp.redhat.com (Postfix) with ESMTP id E37D5492C14; Fri, 7 Apr 2023 02:24:23 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: catalin.marinas@arm.com, horms@kernel.org, thunder.leizhen@huawei.com, John.p.donnelly@oracle.com, will@kernel.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Baoquan He Subject: [PATCH v5] arm64: kdump: simplify the reservation behaviour of crashkernel=,high Date: Fri, 7 Apr 2023 10:24:19 +0800 Message-Id: <20230407022419.19412-1-bhe@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230406_192437_052587_9C2D1AC9 X-CRM114-Status: GOOD ( 21.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On arm64, reservation for 'crashkernel=xM,high' is taken by searching for suitable memory region top down. If the 'xM' of crashkernel high memory is reserved from high memory successfully, it will try to reserve crashkernel low memory later accoringly. Otherwise, it will try to search low memory area for the 'xM' suitable region. Please see the details in Documentation/admin-guide/kernel-parameters.txt. While we observed an unexpected case where a reserved region crosses the high and low meomry boundary. E.g on a system with 4G as low memory end, user added the kernel parameters like: 'crashkernel=512M,high', it could finally have [4G-126M, 4G+386M], [1G, 1G+128M] regions in running kernel. The crashkernel high region crossing low and high memory boudary will bring issues: 1) For crashkernel=x,high, if getting crashkernel high region across low and high memory boundary, then user will see two memory regions in low memory, and one memory region in high memory. The two crashkernel low memory regions are confusing as shown in above example. 2) If people explicityly specify "crashkernel=x,high crashkernel=y,low" and y <= 128M, when crashkernel high region crosses low and high memory boundary and the part of crashkernel high reservation below boundary is bigger than y, the expected crahskernel low reservation will be skipped. But the expected crashkernel high reservation is shrank and could not satisfy user space requirement. 3) The crossing boundary behaviour of crahskernel high reservation is different than x86 arch. On x86_64, the low memory end is 4G fixedly, and the memory near 4G is reserved by system, e.g for mapping firmware, pci mapping, so the crashkernel reservation crossing boundary never happens. From distros point of view, this brings inconsistency and confusion. Users need to dig into x86 and arm64 system details to find out why. For kernel itself, the impact of issue 3) could be slight. While issue 1) and 2) cause actual impact because it brings obscure semantics and behaviour to crashkernel=,high reservation. Here, for crashkernel=xM,high, search the high memory for the suitable region only in high memory. If failed, try reserving the suitable region only in low memory. Like this, the crashkernel high region will only exist in high memory, and crashkernel low region only exists in low memory. The reservation behaviour for crashkernel=,high is clearer and simpler. Note: RPi4 has different zone ranges than normal memory. Its DMA zone is 0~1G, and DMA32 zone is 1G~4G if CONFIG_ZONE_DMA|DMA32 are enabled by default. The low memory end is 1G in order to validate all devices, high memory starts at 1G memory. However, for being consistent with normla arm64 system, its low memory end is still 1G, while reserving crashkernel high memory from 4G if crashkernel=size,high specified. This will remove confusion. With above change applied, summary of arm64 crashkernel reservation range: 1) RPi4(zone DMA:0~1G; DMA32:1G~4G): crashkernel=size 0~1G: low memory | 1G~top: high memory crashkernel=size,high 0~1G: low memory | 4G~top: high memory 2) Other normal system: crashkernel=size crashkernel=size,high 0~4G: low memory | 4G~top: high memory 3) Systems w/o zone DMA|DMA32 crashkernel=size crashkernel=size,high 0~top: low memory Signed-off-by: Baoquan He Reviewed-by: Catalin Marinas Signed-off-by: Baoquan He --- arch/arm64/mm/init.c | 44 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 34 insertions(+), 10 deletions(-) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 66e70ca47680..307263c01292 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -69,6 +69,7 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit; #define CRASH_ADDR_LOW_MAX arm64_dma_phys_limit #define CRASH_ADDR_HIGH_MAX (PHYS_MASK + 1) +#define CRASH_HIGH_SEARCH_BASE SZ_4G #define DEFAULT_CRASH_KERNEL_LOW_SIZE (128UL << 20) @@ -101,12 +102,13 @@ static int __init reserve_crashkernel_low(unsigned long long low_size) */ static void __init reserve_crashkernel(void) { - unsigned long long crash_base, crash_size; - unsigned long long crash_low_size = 0; + unsigned long long crash_base, crash_size, search_base; unsigned long long crash_max = CRASH_ADDR_LOW_MAX; + unsigned long long crash_low_size = 0; char *cmdline = boot_command_line; - int ret; bool fixed_base = false; + bool high = false; + int ret; if (!IS_ENABLED(CONFIG_KEXEC_CORE)) return; @@ -129,7 +131,9 @@ static void __init reserve_crashkernel(void) else if (ret) return; + search_base = CRASH_HIGH_SEARCH_BASE; crash_max = CRASH_ADDR_HIGH_MAX; + high = true; } else if (ret || !crash_size) { /* The specified value is invalid */ return; @@ -140,31 +144,51 @@ static void __init reserve_crashkernel(void) /* User specifies base address explicitly. */ if (crash_base) { fixed_base = true; + search_base = crash_base; crash_max = crash_base + crash_size; } retry: crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, - crash_base, crash_max); + search_base, crash_max); if (!crash_base) { /* - * If the first attempt was for low memory, fall back to - * high memory, the minimum required low memory will be - * reserved later. + * For crashkernel=size[KMG]@offset[KMG], print out failure + * message if can't reserve the specified region. */ - if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) { + if (fixed_base) { + pr_warn("crashkernel reservation failed - memory is in use.\n"); + return; + } + + /* + * For crashkernel=size[KMG], if the first attempt was for + * low memory, fall back to high memory, the minimum required + * low memory will be reserved later. + */ + if (!high && crash_max == CRASH_ADDR_LOW_MAX) { crash_max = CRASH_ADDR_HIGH_MAX; + search_base = CRASH_ADDR_LOW_MAX; crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; goto retry; } + /* + * For crashkernel=size[KMG],high, if the first attempt was + * for high memory, fall back to low memory. + */ + if (high && crash_max == CRASH_ADDR_HIGH_MAX) { + crash_max = CRASH_ADDR_LOW_MAX; + search_base = 0; + goto retry; + } pr_warn("cannot allocate crashkernel (size:0x%llx)\n", crash_size); return; } - if ((crash_base > CRASH_ADDR_LOW_MAX - crash_low_size) && - crash_low_size && reserve_crashkernel_low(crash_low_size)) { + if ((crash_base >= CRASH_ADDR_LOW_MAX) && crash_low_size && + reserve_crashkernel_low(crash_low_size)) { memblock_phys_free(crash_base, crash_size); return; }