From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) (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 42FF3757EB for ; Tue, 6 Aug 2024 02:19:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.35 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722910769; cv=none; b=dOwlhMR/Z6QNw278TcNuYLgIYlu6ZCa1ERtzINPMZOg22XPo6IW1BYaApCms3TWXWOAdH7sxjDKxz04QJNbGdfh7ExGYAAkd7w0Y14+wL3Gky8jNoPIj5L3LHNjDdLSeJUANRrs3zuMrx004vk8X/k4K/R5rfeaY2ZTwm1UHAZM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722910769; c=relaxed/simple; bh=SgCaGlYNwtKWWvSGFawFuAHR/Xo3DceOjircE0tpmyY=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=jtWAYrZA6G4bT5mTb7Zk0j0B8satt0Tb+eyjYAx3q0CWYTGM+FmweKsHfzYGlUKNaYWOBRHLyVyhhEb6kwDvhUoljcz+hVtRp52UH0f9d3mPml4YYo2Sfu6XQV2Ag3gfo6Kp8E78cVE9AJYb9YT7Iv7BSaTKuW2/JUFI58HNAlU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.35 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4WdH1k5m0mz1S75v; Tue, 6 Aug 2024 10:14:34 +0800 (CST) Received: from kwepemi100008.china.huawei.com (unknown [7.221.188.57]) by mail.maildlp.com (Postfix) with ESMTPS id 5E3911402CF; Tue, 6 Aug 2024 10:19:16 +0800 (CST) Received: from [10.67.109.254] (10.67.109.254) by kwepemi100008.china.huawei.com (7.221.188.57) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Tue, 6 Aug 2024 10:19:15 +0800 Message-ID: <93bbedcd-2f6b-3124-6b54-01080efeb515@huawei.com> Date: Tue, 6 Aug 2024 10:19:14 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [RFC PATCH] ARM: Support allocating crashkernel above 4G for LPAE Content-Language: en-US To: Catalin Marinas , "Russell King (Oracle)" CC: , , , References: <20240802092510.3915986-1-ruanjinjie@huawei.com> From: Jinjie Ruan In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemi100008.china.huawei.com (7.221.188.57) On 2024/8/5 21:18, Catalin Marinas wrote: > On Fri, Aug 02, 2024 at 12:01:43PM +0100, Russell King wrote: >> On Fri, Aug 02, 2024 at 05:25:10PM +0800, Jinjie Ruan wrote: >>> As ARM LPAE feature support accessing memory beyond the 4G limit, define >>> HAVE_ARCH_CRASHKERNEL_RESERVATION_HIGH macro to support reserving crash > > At least in 6.11-rc1, there's no trace of such macro anywhere. So not > sure this patch has any effect (I haven't checked linux-next though). Sorry, this macro is introduced in linux-next, the -next subject has been missed. > >>> memory above 4G for ARM32 LPAE. >>> >>> No test because there is no LPAE ARM32 hardware. >> >> Why are you submitting patches for features you can't test? >> >> I'm not going to apply this without it being properly tested, because I >> don't believe that this will work in the generic case. >> >> If the crash kernel is located in memory outside of the lower 4GiB of >> address space, and there is no alias within physical address space >> for that memory, then there is *no* *way* for such a kernel to boot. >> >> So, right now I believe this patch to be *fundamentally* wrong. > > Indeed. Even on arm64, we keep some crashkernel reservations in the > lower parts of the memory for ZONE_DMA allocations. Indeed, it is. > > On arch/arm with LPAE, we could do something similar like forcing some > lowmem reservation and allowing explicit allocation in the higher ranges > with crashkernel=,high. We should, of course, force the kdump In linux-next, with the HAVE_ARCH_CRASHKERNEL_RESERVATION_HIGH macro defined, it is ok. > image placement in the lower memory. The user kexec tools must be taught > to interpret this information and provide a DT accordingly to the crash > kernel. >