From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hHRB9-000221-Hh for kexec@lists.infradead.org; Fri, 19 Apr 2019 10:55:36 +0000 Date: Fri, 19 Apr 2019 18:55:29 +0800 From: Baoquan He Subject: Re: [RFC PATCH] kexec, x86/boot: map systab region in identity mapping before accessing it Message-ID: <20190419105529.GF11060@MiWiFi-R3L-srv> References: <20190419101733.GA10324@zn.tnic> <20190419105014.GE11060@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190419105014.GE11060@MiWiFi-R3L-srv> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Borislav Petkov Cc: "x86@kernel.org" , Kairui Song , Chao Fan , "kexec@lists.infradead.org" , linux-kernel@vger.kernel.org, Junichi Nomura , Thomas Gleixner , Dave Young On 04/19/19 at 06:50pm, Baoquan He wrote: > On 04/19/19 at 12:17pm, Borislav Petkov wrote: > > Breaking thread because this one got too big. > > > > On Fri, Apr 19, 2019 at 04:34:58PM +0800, Kairui Song wrote: > > > There are two approach to fix it, detect if the systab is mapped, and > > > avoid reading it if not. > > > > Ok, so tglx and I discussed this situation which is slowly getting out > > of hand with all the tinkering. > > > > So, here's what we should do - scream loudly now if some of this doesn't > > make any sense. > > > > 1. Junichi's patch should get the systab check above added and sent to > > 5.1 so that at least some EFI kexecing can work with 5.1 > > Talked with Kairui privately just now. Seems Junichi's patch need add > this systab mapping. Since the systab region is not mapped on some > machines. Those machine don't have this issue because they got systab > region luckily coverred by 1 GB page mapping in 1st kernel before > kexec jumping. > > This issue should happen whether it is KASLR kernel or not KASLR kernel. > > > > > 2. Then, the fact whether the kernel has been kexec'ed and which > > addresses it should use early, should all be passed through boot_params > > which is either setup by kexec(1) or by the first kernel itself, in the > > kexec_file_load() case. > > Seems no better way to check if it's kexec-ed kernel, except of the > setup data checking of kexec-ed kernel. > > It may happen in both kexec_load or kexec_file_load, since we build > ident mapping of kexec for RAM in 1st kernel. > > > > > > the systab region is not mapped by the identity mapping provided by > > > kexec. > > > > 3. Then that needs to be fixed in the first kernel as it is a > > shortcoming of us starting to parse systab very early. It is the kexec > > setup code's problem not the early compressed stage's problem that the > > EFI systab is not mapped. > > Yeah, adding the systab mapping looks good. Kairui put it in ^ in 1st kernel > 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. > > Thanks > Baoquan _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec