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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A11FAC10F13 for ; Thu, 11 Apr 2019 08:42:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 758B8218AE for ; Thu, 11 Apr 2019 08:42:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726830AbfDKIml (ORCPT ); Thu, 11 Apr 2019 04:42:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54590 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726139AbfDKIml (ORCPT ); Thu, 11 Apr 2019 04:42:41 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 342D23007452; Thu, 11 Apr 2019 08:42:41 +0000 (UTC) Received: from localhost (ovpn-12-112.pek2.redhat.com [10.72.12.112]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2231D5D961; Thu, 11 Apr 2019 08:42:37 +0000 (UTC) Date: Thu, 11 Apr 2019 16:42:35 +0800 From: Baoquan He To: Junichi Nomura Cc: Borislav Petkov , Dave Young , Chao Fan , Kairui Song , "x86@kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel Message-ID: <20190411084235.GJ3805@localhost.localdomain> References: <20190408231011.GA5402@jeru.linux.bs1.fc.nec.co.jp> <20190410171431.GE26580@zn.tnic> <7cbc096d-0548-18b1-a335-8ba114f234a7@ce.jp.nec.com> <20190411080927.GA30080@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 11 Apr 2019 08:42:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/11/19 at 08:16am, Junichi Nomura wrote: > On 4/11/19 5:09 PM, Borislav Petkov wrote: > > On Wed, Apr 10, 2019 at 11:34:51PM +0000, Junichi Nomura wrote: > >> But efi_get_rsdp_addr() needs to check whether the kernel was > >> kexec booted to avoid accessing invalid EFI table address. > >> efi_get_kexec_setup_data_addr() is the only method I know > >> to check if it was kexec-booted. > > > > Your v3 had the right approach - you first check if you can get the > > address as a kexec-ed kernel. If you do, you use that one and continue > > the normal path. > > > > If you don't, you fall back to efi_get_rsdp_addr() and get it directly > > from EFI. > > > > And then carve out the functionality you need to call multiple times in > > helper functions like __efi_get_rsdp_addr(). > > > > Why doesn't that work anymore? > > kexec_get_rsdp_addr() might fail on kexec-booted kernel, e.g. if the > setup_data was invalid. In such a case, falling back to efi_get_rsdp_addr() > will hit the problem of accessing invalid table pointer again. Seems you are trying to address Dave Young's comment in http://lkml.kernel.org/r/20190404073233.GC5708@dhcp-128-65.nay.redhat.com We may need discuss and make clear if those are doable. E.g the first comment, if not hang by below line of code, returning 0 for what? Can kexec still be saved, or just reset to firmware? error("EFI system table not found in kexec boot_params.") It may need be clarified firstly, then go further to rearrange patch. That can ease the work, I guess. Personal opinion. Thanks Baoquan 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 1hEVIA-0000TT-2d for kexec@lists.infradead.org; Thu, 11 Apr 2019 08:42:43 +0000 Date: Thu, 11 Apr 2019 16:42:35 +0800 From: Baoquan He Subject: Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel Message-ID: <20190411084235.GJ3805@localhost.localdomain> References: <20190408231011.GA5402@jeru.linux.bs1.fc.nec.co.jp> <20190410171431.GE26580@zn.tnic> <7cbc096d-0548-18b1-a335-8ba114f234a7@ce.jp.nec.com> <20190411080927.GA30080@zn.tnic> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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: Junichi Nomura Cc: Chao Fan , Kairui Song , "x86@kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Borislav Petkov , Dave Young On 04/11/19 at 08:16am, Junichi Nomura wrote: > On 4/11/19 5:09 PM, Borislav Petkov wrote: > > On Wed, Apr 10, 2019 at 11:34:51PM +0000, Junichi Nomura wrote: > >> But efi_get_rsdp_addr() needs to check whether the kernel was > >> kexec booted to avoid accessing invalid EFI table address. > >> efi_get_kexec_setup_data_addr() is the only method I know > >> to check if it was kexec-booted. > > > > Your v3 had the right approach - you first check if you can get the > > address as a kexec-ed kernel. If you do, you use that one and continue > > the normal path. > > > > If you don't, you fall back to efi_get_rsdp_addr() and get it directly > > from EFI. > > > > And then carve out the functionality you need to call multiple times in > > helper functions like __efi_get_rsdp_addr(). > > > > Why doesn't that work anymore? > > kexec_get_rsdp_addr() might fail on kexec-booted kernel, e.g. if the > setup_data was invalid. In such a case, falling back to efi_get_rsdp_addr() > will hit the problem of accessing invalid table pointer again. Seems you are trying to address Dave Young's comment in http://lkml.kernel.org/r/20190404073233.GC5708@dhcp-128-65.nay.redhat.com We may need discuss and make clear if those are doable. E.g the first comment, if not hang by below line of code, returning 0 for what? Can kexec still be saved, or just reset to firmware? error("EFI system table not found in kexec boot_params.") It may need be clarified firstly, then go further to rearrange patch. That can ease the work, I guess. Personal opinion. Thanks Baoquan _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec