Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751140AbWBLQc5 (ORCPT ); Sun, 12 Feb 2006 11:32:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751141AbWBLQc5 (ORCPT ); Sun, 12 Feb 2006 11:32:57 -0500 Received: from smtpout.mac.com ([17.250.248.86]:55256 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id S1751140AbWBLQc4 (ORCPT ); Sun, 12 Feb 2006 11:32:56 -0500 In-Reply-To: <43EF24C0.2040902@gmail.com> References: <20060201113710.6320.68289.stgit@localhost.localdomain> <200602101337.22078.rjw@sisk.pl> <20060210233507.GC1952@elf.ucw.cz> <200602111136.56325.merka@highsphere.net> <43EEF711.2010409@gmail.com> <43833C9D-40A2-42B3-83D9-3C9D3EB7C434@mac.com> <43EF24C0.2040902@gmail.com> Mime-Version: 1.0 (Apple Message framework v746.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <47B33C16-AEC3-4036-BA05-AE235014684E@mac.com> Cc: Jan Merka , Pavel Machek , suspend2-devel@lists.suspend2.net, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit From: Kyle Moffett Subject: Re: Flames over -- Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.) Date: Sun, 12 Feb 2006 11:32:44 -0500 To: Alon Bar-Lev X-Mailer: Apple Mail (2.746.2) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6822 Lines: 150 On Feb 12, 2006, at 07:06, Alon Bar-Lev wrote: > Kyle Moffett wrote: >> Why the hell would you even _want_ to encrypt data in RAM? If you >> have a secure OS install and a passworded screensaver that starts >> before suspend, then there is _nothing_ an attacker could do to >> the contents of RAM without hard-booting, which would just >> completely erase it, or without extremely specialized hardware and >> expertise. Picking up a machine suspended to RAM is just as >> secure as picking up one that is on, no more or less. > > I guess you are not a security aware user... A machine that is > turned on is *MUCH* less secured than a machine which is turned off > and have its disks encrypted. We can start argue on this issue > too... But I won't cooperate... Where is your proof? This is quite true for a machine on a _network_, but my suspended laptop isn't. You say that I am not a security aware user and that therefore you are automatically right, but it doesn't make it so. What is the practical vulnerability in my laptop's suspend-to-ram, given that it automatically locks all VTs and X when sleeping? Don't you *dare* say "somebody could attach a hardware debugger and read your data out of RAM", because I just don't see that happening in any reasonable situation, there are too many obstacles to doing that with a _laptop_, the first of which is just that it's impossible to take the damn thing apart when it's on without disconnecting massive amounts of critical wiring. Even if that _is_ a risk-case for you, it's not the use-case we should optimize suspend for! >>> And another fact: Suspend-to-RAM implementation can be derived >>> form suspend-to-disk but not the other way around. >> >> No, the two are _entirely_ independent. Suspend-to-RAM does not >> need to copy memory at all, whereas suspend-to-disk requires it. >> That very fact means that suspend-to-RAM is orders of magnitude >> faster than suspend-to-disk could ever be, especially as RAM gets >> exponentially larger. > > Well... I see you already planned the implementation and have all > figured out... But the fact is that suspend-to-RAM can be > implemented by suspend-to-disk without actually store the memory to > external device... Right, the process goes something like this pseudocode: put_devices_to_sleep(); /* [1] */ if (suspend_to_ram) { call_firmware_suspend(); } else { atomically_freeze_state(); wake_devices_up(); store_state_to_devices(); /* [2] */ put_devices_to_sleep(); switch(mode) { SUSP_SHUTDOWN: shutdown(); SUSP_REBOOT: reboot(); [.......................] } } Remind me again why we should implement suspend-to-RAM as part of suspend-to-disk? Especially since the _only_ shared functionality is [1] which is already separated out for other reasons. A lot of people also seem to want to initiate and control all of [2] in userspace, whereas the suspend-to-RAM case needs just one syscall. > But hay... You can implement and maintain two separate solutions... You still have yet to prove that suspend-to-RAM and suspend-to-disk have anything to gain by being wrapped in a big if statement. >> No, suspend-to-ram is for people who need instant response times, >> suspend-to-disk should be an extension or simplification of >> "Freeze a process tree and all associated system status so we can >> completely give up the hardware for a while". IMHO, the fact that >> both are called "suspend" is just due to historical quirk as >> opposed to any real similarity. > > Again... This is a matter of implementation... I believe that one > complete suspend implementation can suite both disk and RAM... The > only difference is if you write the state to external storage, and > how you play with APM. So there is a good reason why both are > called "suspend". > > I don't claim that virtualization approach is not appropriate, and > in the future suspend may use this in order to create its snapshot, > and maybe, as you say, you may get suspend-to-RAM in-kernel and > suspend-to-disk in user-space by dumping each process's container > into a file (I don't know what you do with graphics and caching... > but let's assume you have solution for all). > > Let's see what happened so far: > > First we had swsusp... For many people it did not work, so Suspend2 > was developed, but was not merged mainly because it had too many UI > components in-kernel. Actually, I seem to recall that even before _either_ of those were working decently a bunch of modern hardware had good suspend-to-RAM support. > Then comes the micro-kernel approach to convert swsusp into > uswsusp... Suspend2 which is stable now cannot be merged since it > violates this idea. So users will not get a proper merged solution > for at least one more year. > > Now, you come with a different solution (virtualization), so let's > delay suspend feature for how long? At least two years? Personally, I really don't care if you (or whoever) wants to merge an intermediate suspend-to-disk/software-suspend implementation. I think it would be helpful on a lot of laptops where suspend-to-RAM doesn't work or chews battery. But I _really_ don't want to see somebody trying to patch suspend-to-RAM/hardware-suspend into that mess. > We need (and can get) suspend to work *NOW*, It does work now, suspend-to-RAM/hardware-suspend has been working perfectly on my laptop for a long time (modulo a couple powerbook USB bugs that crept in recently and got removed). IMHO, a modern laptop that doesn't support suspend-to-RAM is a broken design, although I realize that it happens all too often. > laptops are being more and more common... People expect to have > this ability in a modern operating system, they don't care if it is > implemented in kernel or in user-space, they also don't care if you > change it along the way... And if in the future Linux will be pure > virtual machine, all will be happy.... And use it... But please > consider offering a working solution *NOW*. On this I do agree, but _please_ don't muck with my suspend-to-RAM along the way because of some egotistical "We are new-fancy-kernel- software-suspend, resistance is futile" type thing, ok? Suspend-to- RAM/hardware-suspend and suspend-to-disk/software-suspend are two _completely_ different things and should not be treated the same at all. Cheers, Kyle Moffett -- Premature optimization is the root of all evil in programming -- C.A.R. 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