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 23A9CC52D6F for ; Tue, 6 Aug 2024 11:03:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=dG/wdq4KNgGfbSlTIoCrxrVcBX6174acHdMyq7P0THM=; b=efNbrrRn1JSRSDR3AJS71gC4Hi Lu+Mz5Z3akD0diB3+gNHu30t+TAtdoI+YmYJLKwUt7QB6OSL5Mt+ZaDkHU1amUqDrVpqJ1GkAYB7P bWgcWu/RZW3tJmtCtzd/2vhZuCe8dxNnC6WUWSb+Xyoh03PyzvzQuv+WvseddefEUb0MwJOsAadUc 3geCan5zEuTZTBuzwbiajM9QblEzdSpdGpEiPSvVM/tGHjoVIMZ5ocjxPt6HuBFUOnF0BS/UgRK0g qW7kgjUyDyOO4LL8qSWqM7zqqwoFONjFjGM43ZYkmd1tWkZtNkrO5qo72jptqTRTWQANFtZ1pJs+I XRMx8org==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbHy8-00000001IYy-3u6N; Tue, 06 Aug 2024 11:03:08 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbHxc-00000001IQq-0Aco for linux-arm-kernel@lists.infradead.org; Tue, 06 Aug 2024 11:02:37 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722942154; 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; bh=dG/wdq4KNgGfbSlTIoCrxrVcBX6174acHdMyq7P0THM=; b=P+fcUeoa+ax6iNWdbEbGICFPaPKERJy9JjCU/Oj2Ta9e8VIbh3UFmH3Q4GJ4gsiqAcP/bd gRCArJbjUNDEdSaOEXp4KpVJdimCiibGWK1p1WO9/z+c1t3SR1wcC6zLA7WwBapplL8bcW Y26+Nce0a93ZNey36W5L4GaVu5dspks= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-396-jCS_w4KXPe60S2XtvRMnDA-1; Tue, 06 Aug 2024 07:02:33 -0400 X-MC-Unique: jCS_w4KXPe60S2XtvRMnDA-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CCB6B1955D44; Tue, 6 Aug 2024 11:02:31 +0000 (UTC) Received: from localhost (unknown [10.72.112.21]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8128319560AE; Tue, 6 Aug 2024 11:02:29 +0000 (UTC) Date: Tue, 6 Aug 2024 19:02:20 +0800 From: Baoquan He To: "Russell King (Oracle)" Cc: Jinjie Ruan , akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] ARM: Support allocating crashkernel above 4G for LPAE Message-ID: References: <20240802092510.3915986-1-ruanjinjie@huawei.com> <6c0a45c3-08a2-f889-9e66-ab8aff66ae8c@huawei.com> <8f051483-46be-87b6-03bb-5e0d145a2ac3@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240806_040236_261797_FFF10958 X-CRM114-Status: GOOD ( 20.91 ) 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 08/06/24 at 09:34am, Russell King (Oracle) wrote: > On Tue, Aug 06, 2024 at 04:11:30PM +0800, Baoquan He wrote: > > I am fine with it. BUT have you addressed Russell's concern, e.g how to > > test it actually? > > Thanks for bringing that up. > > Let me reinforce my position on this. I will _not_ be accepting a patch > that allows the crash kernel to be placed into high memory on 32-bit > ARM unless it has been thoroughly tested to prove that it can actually > work. > > Right now, I don't believe it can work as placing the kernel in highmem > likely means it will be located *outside* of the lower 4GiB of physical > memory which is all that will be accessible when the MMU is turned off. > This is a pre-condition to boot a kernel - the kernel image _must_ be > located within a region of memory which is exposed to the CPU when the > MMU is turned off. > > Unless it can be proven that placing the kernel in highmem means that > the kernel will be located in the lower 4GiB of physical memory space > with the MMU off, then further work on this patch is a waste of time. Yeah, totally agree.