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[209.132.180.67]) by mx.google.com with ESMTP id q86si6125537pfi.197.2019.04.19.11.55.04; Fri, 19 Apr 2019 11:55:19 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728534AbfDSSxb (ORCPT + 99 others); Fri, 19 Apr 2019 14:53:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53490 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728513AbfDSSxa (ORCPT ); Fri, 19 Apr 2019 14:53:30 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 52F4830917F0; Fri, 19 Apr 2019 11:44:27 +0000 (UTC) Received: from localhost (ovpn-12-186.pek2.redhat.com [10.72.12.186]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ACE3A5D70D; Fri, 19 Apr 2019 11:44:24 +0000 (UTC) Date: Fri, 19 Apr 2019 19:44:21 +0800 From: Baoquan He To: Borislav Petkov Cc: Kairui Song , Thomas Gleixner , linux-kernel@vger.kernel.org, Junichi Nomura , Dave Young , Chao Fan , "x86@kernel.org" , "kexec@lists.infradead.org" Subject: Re: [RFC PATCH] kexec, x86/boot: map systab region in identity mapping before accessing it Message-ID: <20190419114421.GH11060@MiWiFi-R3L-srv> References: <20190419101733.GA10324@zn.tnic> <20190419105014.GE11060@MiWiFi-R3L-srv> <20190419112801.GB10324@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190419112801.GB10324@zn.tnic> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Fri, 19 Apr 2019 11:44:27 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/19/19 at 01:28pm, Borislav Petkov wrote: > Why does that "seem" so? > > Read again what I said: "should all be passed through boot_params". > Which means, boot_params should be extended with a field of a flag to > say: "this is a kexec'ed kernel". > > If it "seems" then it should be made to not "seem" but to work properly. No objection to extending with fields of a flag to mark kexec'ed kernel. Or kdump kernel either. We now check kdump kernel by /proc/vmcore. > > > Yeah, adding the systab mapping looks good. Kairui put it in > > decompressing stage just because he wants to cover the case in which the > > old kernel kexec jumping to 2nd kernel. Now it seems not very > > reasonable, we also have the new kernel kexec jumping to old 2nd kernel. > > I don't think we can guarantee kexec between old<->new kernel to always > work. Otherwise, we can forget all development and improvements of new > kernel. I personally agree with this. Very earlier, we tried to remove the 896 MB limitation of crashkernel=xM, to extend it to 4G or the whole RAM, but rejcted by linus since he worried it could break the old kernel kdumping. I may not remember well.