From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mga14.intel.com ([143.182.124.37]) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1JwrqG-0005Ly-FV for kexec@lists.infradead.org; Fri, 16 May 2008 04:46:52 +0000 Subject: Re: [PATCH] kexec based hibernation: a prototype of kexec multi-stage load From: "Huang, Ying" In-Reply-To: References: <1210574441.30365.8.camel@caritas-dev.intel.com> <20080513053408.GA5870@redhat.com> <1210730266.23707.50.camel@caritas-dev.intel.com> <20080514025607.GA19944@redhat.com> <1210736275.23707.62.camel@caritas-dev.intel.com> <1210827473.23707.133.camel@caritas-dev.intel.com> <20080516020043.GC6926@redhat.com> <1210904374.23707.178.camel@caritas-dev.intel.com> Date: Fri, 16 May 2008 12:52:48 +0800 Message-ID: <1210913568.23707.230.camel@caritas-dev.intel.com> MIME-Version: 1.0 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-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: "Eric W. Biederman" Cc: nigel@nigel.suspend2.net, Kexec Mailing List , linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Pavel Machek , Andrew Morton , Vivek Goyal On Thu, 2008-05-15 at 19:55 -0700, Eric W. Biederman wrote: > "Huang, Ying" writes: > > > The disadvantage of this solution is that kernel B must know it is > > original kernel (A) or kexeced kernel (B). Different code should be used > > by kernel A and kernel B. And after jump from A to B, jump from B to A, > > when jump from A to B again, kernel A must use different code from the > > first time. > > I don't know what the case is for keeping two kernels in memory and switching > between them. This can be used to save the memory image of kernel B and accelerate the hibernation. The real boot of kernel B is only needed first time. > I suspect a small piece of trampoline code between the two kernels could > handle the case. (i.e. purgatory pays attention). > > That is a fundamental aspect of the design. A general purpose infrastructure > with trampoline code to adapt it to whatever situation comes up. It is possible to use purgatory to deal with this problem. Jump from kernel A to kernel B Jump to entry of purgatory (purgatory_entry) purgatory save the return address (kexec_jump_back_entry_A) Purgatory set kexec_jump_back_entry for kernel B to a code segment in purgatory, say kexec_jump_back_entry_A_for_B Purgatory jump to entry point of kernel B Jump from kernel B to kernel A Jump to purgatory (kexec_jump_back_entry_A_for_B) Purgatory save the return address (kexec_jump_back_entry_B) Purgatory return to kernel A (kexec_jump_back_entry_A) Jump from kernel A to kernel B again Jump to entry of purgatory (purgatory_entry) Purgatory save the return address (kexec_jump_back_entry_A) Purgatory jump to kexec_jump_back_entry_B The disadvantage of this solution is that some information is saved in purgatory (kexec_jump_back_entry_A, kexec_jump_back_entry_B). So, purgatory must be saved too when save the memory image of kernel A or kernel B. Purgatory can be seen as a part of kernel B. But it is a little tricky to think it as a part of kernel A too. Best Regards, Huang Ying _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755979AbYEPErB (ORCPT ); Fri, 16 May 2008 00:47:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751419AbYEPEqw (ORCPT ); Fri, 16 May 2008 00:46:52 -0400 Received: from mga14.intel.com ([143.182.124.37]:34526 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017AbYEPEqv (ORCPT ); Fri, 16 May 2008 00:46:51 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.27,495,1204531200"; d="scan'208";a="247683538" Subject: Re: [PATCH] kexec based hibernation: a prototype of kexec multi-stage load From: "Huang, Ying" To: "Eric W. Biederman" CC: Vivek Goyal , Pavel Machek , nigel@nigel.suspend2.net, "Rafael J. Wysocki" , Andrew Morton , linux-kernel@vger.kernel.org, Kexec Mailing List In-Reply-To: References: <1210574441.30365.8.camel@caritas-dev.intel.com> <20080513053408.GA5870@redhat.com> <1210730266.23707.50.camel@caritas-dev.intel.com> <20080514025607.GA19944@redhat.com> <1210736275.23707.62.camel@caritas-dev.intel.com> <1210827473.23707.133.camel@caritas-dev.intel.com> <20080516020043.GC6926@redhat.com> <1210904374.23707.178.camel@caritas-dev.intel.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 16 May 2008 12:52:48 +0800 Message-ID: <1210913568.23707.230.camel@caritas-dev.intel.com> MIME-Version: 1.0 X-Mailer: Evolution 2.22.1 X-OriginalArrivalTime: 16 May 2008 04:46:17.0547 (UTC) FILETIME=[C74269B0:01C8B70F] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2008-05-15 at 19:55 -0700, Eric W. Biederman wrote: > "Huang, Ying" writes: > > > The disadvantage of this solution is that kernel B must know it is > > original kernel (A) or kexeced kernel (B). Different code should be used > > by kernel A and kernel B. And after jump from A to B, jump from B to A, > > when jump from A to B again, kernel A must use different code from the > > first time. > > I don't know what the case is for keeping two kernels in memory and switching > between them. This can be used to save the memory image of kernel B and accelerate the hibernation. The real boot of kernel B is only needed first time. > I suspect a small piece of trampoline code between the two kernels could > handle the case. (i.e. purgatory pays attention). > > That is a fundamental aspect of the design. A general purpose infrastructure > with trampoline code to adapt it to whatever situation comes up. It is possible to use purgatory to deal with this problem. Jump from kernel A to kernel B Jump to entry of purgatory (purgatory_entry) purgatory save the return address (kexec_jump_back_entry_A) Purgatory set kexec_jump_back_entry for kernel B to a code segment in purgatory, say kexec_jump_back_entry_A_for_B Purgatory jump to entry point of kernel B Jump from kernel B to kernel A Jump to purgatory (kexec_jump_back_entry_A_for_B) Purgatory save the return address (kexec_jump_back_entry_B) Purgatory return to kernel A (kexec_jump_back_entry_A) Jump from kernel A to kernel B again Jump to entry of purgatory (purgatory_entry) Purgatory save the return address (kexec_jump_back_entry_A) Purgatory jump to kexec_jump_back_entry_B The disadvantage of this solution is that some information is saved in purgatory (kexec_jump_back_entry_A, kexec_jump_back_entry_B). So, purgatory must be saved too when save the memory image of kernel A or kernel B. Purgatory can be seen as a part of kernel B. But it is a little tricky to think it as a part of kernel A too. Best Regards, Huang Ying