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 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 4F4E9C05027 for ; Fri, 20 Jan 2023 09:06:33 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=OGUZVnNc2ggI/NeSTPB+yk6yEd7jK7qGfOqKRV2MY80=; b=WBDg/s7rum8nLL kAPm4EDAMdTvC/r2g0O+DbKrlh+fc+dGAC8o8mktcbkewvaqmGMKoU28JAJPWP1oWDbz2eLGjufHM hWmFdCV7ptyfnccm38safaldb/ohkFjhneBcV0gr24ocoqcNcC5TkyG+YEPwLo1bw+1pzpqB3NE8H YiEnHGvw7PX26kzbbIdOtsHRyYsPRByqtA5QxQh+Goa/sy6LTa49XK2/zY6kLVuCq82RmZHs0FXem n+KrnwzTiZL8K2E3Q0Mp3JdW8iFp4ksbzurcHshUWVh5W+oLOfxNPu+GJWIFXBi79HRn/XE9uioOI LtNGblrKeZF70d/8o+Kw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pInL2-009CT1-3a; Fri, 20 Jan 2023 09:05:32 +0000 Received: from zeeaster.vergenet.net ([206.189.110.174]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pInKw-009CR4-FH; Fri, 20 Jan 2023 09:05:28 +0000 Received: from momiji.horms.nl (2a02-a46e-7b6b-703-d63d-7eff-fe99-ac9d.fixed6.kpn.net [IPv6:2a02:a46e:7b6b:703:d63d:7eff:fe99:ac9d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by zeeaster.vergenet.net (Postfix) with ESMTPSA id AFDB420099; Fri, 20 Jan 2023 09:04:50 +0000 (UTC) Received: by momiji.horms.nl (Postfix, from userid 7100) id 4606D94030F; Fri, 20 Jan 2023 10:04:49 +0100 (CET) Date: Fri, 20 Jan 2023 10:04:49 +0100 From: Simon Horman To: Baoquan He Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, thunder.leizhen@huawei.com, John.p.donnelly@oracle.com, wangkefeng.wang@huawei.com Subject: Re: [PATCH 1/2] arm64: kdump: simplify the reservation behaviour of crashkernel=,high Message-ID: References: <20230117034921.185150-1-bhe@redhat.com> <20230117034921.185150-2-bhe@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230117034921.185150-2-bhe@redhat.com> Organisation: Horms Solutions BV X-Virus-Scanned: clamav-milter 0.103.7 at zeeaster X-Virus-Status: Clean X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230120_010526_707702_632A6893 X-CRM114-Status: GOOD ( 30.70 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jan 17, 2023 at 11:49:20AM +0800, Baoquan He wrote: > On arm64, reservation for 'crashkernel=xM,high' is taken by searching for > suitable memory region up 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. > > 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. > This looks very strange because we have two low memory regions > [4G-126M, 4G] and [1G, 1G+128M]. Much explanation need be given to tell > why that happened. > > Here, for crashkernel=xM,high, search the high memory for the suitable > region above the high and low memory boundary. If failed, try reserving > the suitable region below the boundary. 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. > > Signed-off-by: Baoquan He > --- > arch/arm64/mm/init.c | 30 +++++++++++++++++++++++------- > 1 file changed, 23 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 58a0bb2c17f1..26a05af2bfa8 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -127,12 +127,13 @@ 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; > @@ -155,7 +156,9 @@ static void __init reserve_crashkernel(void) > else if (ret) > return; > > + search_base = CRASH_ADDR_LOW_MAX; > crash_max = CRASH_ADDR_HIGH_MAX; > + high = true; > } else if (ret || !crash_size) { > /* The specified value is invalid */ > return; > @@ -166,31 +169,44 @@ 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 (fixed_base) { > + pr_warn("cannot reserve crashkernel region [0x%llx-0x%llx]\n", > + search_base, crash_max); > + return; > + } > + > /* > * If the first attempt was for low memory, fall back to > * high memory, the minimum required low memory will be > * reserved later. > */ > - if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) { > + 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; > } > > + if (high && (crash_max == CRASH_ADDR_HIGH_MAX)) { nit: unnecessary (and inconsistent with code just above) parentheses. > + 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; > } > -- > 2.34.1 > > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel