From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6C0772A1CA for ; Tue, 6 Aug 2024 19:10:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722971435; cv=none; b=clMrs7KOmeDWYKNRmvp2YRTnEI+mMjPMeq26JlVOpo6cqpodxBP5muW5abhCwv3rFeiYuwsqLpQBuWDzTU5bgKY7U3/b5pucrioQX6xUboepHZCsG2rkUfROrpqTs2lWgb3xxuoVp27heA2UlKSig8t7qI5fP14gkfeaYblVBjU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722971435; c=relaxed/simple; bh=z6WPwhGFP8EvUbEwoSFh4HH4xbYWUvjIPysePECmOEA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i4NsWMpOV0MFMmGsZ6dKaMXArZORGitjLBx4AW1CjLXDyj/1LBUepAPseqZq6LDwlGBjRESQ6ohyTOBPR0qKoZmICq0brUPyceR5e/sy/ouLTcrTAc6K4oC76LU/Ewv57Qhz75oJ1WSm4b0WpgUYCZWC7c2fVHCh74AkQZf7nAY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 731ECC32786; Tue, 6 Aug 2024 19:10:32 +0000 (UTC) Date: Tue, 6 Aug 2024 20:10:30 +0100 From: Catalin Marinas To: Baoquan He Cc: Jinjie Ruan , vgoyal@redhat.com, dyoung@redhat.com, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, chenjiahao16@huawei.com, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Will Deacon Subject: Re: [PATCH -next] crash: Fix riscv64 crash memory reserve dead loop Message-ID: References: <20240802090105.3871929-1-ruanjinjie@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: To Jinjie, if you make generic changes that affect other architectures, please either cc the individual lists/maintainers or at least cross-post to linux-arch. I don't follow lkml, there's just too much traffic there. On Fri, Aug 02, 2024 at 06:11:01PM +0800, Baoquan He wrote: > On 08/02/24 at 05:01pm, Jinjie Ruan wrote: > > On RISCV64 Qemu machine with 512MB memory, cmdline "crashkernel=500M,high" > > will cause system stall as below: > > > > Zone ranges: > > DMA32 [mem 0x0000000080000000-0x000000009fffffff] > > Normal empty > > Movable zone start for each node > > Early memory node ranges > > node 0: [mem 0x0000000080000000-0x000000008005ffff] > > node 0: [mem 0x0000000080060000-0x000000009fffffff] > > Initmem setup node 0 [mem 0x0000000080000000-0x000000009fffffff] > > (stall here) > > > > commit 5d99cadf1568 ("crash: fix x86_32 crash memory reserve dead loop > > bug") fix this on 32-bit architecture. However, the problem is not > > completely solved. If `CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX` on 64-bit > > architecture, for example, when system memory is equal to > > CRASH_ADDR_LOW_MAX on RISCV64, the following infinite loop will also occur: > > Interesting, I didn't expect risc-v defining them like these. > > #define CRASH_ADDR_LOW_MAX dma32_phys_limit > #define CRASH_ADDR_HIGH_MAX memblock_end_of_DRAM() arm64 defines the high limit as PHYS_MASK+1, it doesn't need to be dynamic and x86 does something similar (SZ_64T). Not sure why the generic code and riscv define it like this. > > -> reserve_crashkernel_generic() and high is true > > -> alloc at [CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX] fail > > -> alloc at [0, CRASH_ADDR_LOW_MAX] fail and repeatedly > > (because CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX). > > > > Before refactor in commit 9c08a2a139fe ("x86: kdump: use generic interface > > to simplify crashkernel reservation code"), x86 do not try to reserve crash > > memory at low if it fails to alloc above high 4G. However before refator in > > commit fdc268232dbba ("arm64: kdump: use generic interface to simplify > > crashkernel reservation"), arm64 try to reserve crash memory at low if it > > fails above high 4G. For 64-bit systems, this attempt is less beneficial > > than the opposite, remove it to fix this bug and align with native x86 > > implementation. > > And I don't like the idea crashkernel=,high failure will fallback to > attempt in low area, so this looks good to me. Well, I kind of liked this behaviour. One can specify ,high as a preference rather than forcing a range. The arm64 land has different platforms with some constrained memory layouts. Such fallback works well as a default command line option shipped with distros without having to guess the SoC memory layout. Something like below should fix the issue as well (untested): diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c index d3b4cd12bdd1..ae92d6745ef4 100644 --- a/kernel/crash_reserve.c +++ b/kernel/crash_reserve.c @@ -420,7 +420,8 @@ void __init reserve_crashkernel_generic(char *cmdline, * For crashkernel=size[KMG],high, if the first attempt was * for high memory, fall back to low memory. */ - if (high && search_end == CRASH_ADDR_HIGH_MAX) { + if (high && search_end == CRASH_ADDR_HIGH_MAX && + CRASH_ADDR_LOW_MAX < CRASH_ADDR_HIGH_MAX) { search_end = CRASH_ADDR_LOW_MAX; search_base = 0; goto retry; -- Catalin