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xen-devel
Re: [Xen-devel] Several vtpm patches and workarounds: persistence, stabi
Signed-off-by: Matt Fioravante <Matthew.Fioravante@xxxxxxxxxx>
On Fri, 2009-08-21 at 12:33 -0400, Keir Fraser wrote:
> Thanks. Can you provide a signed-off-by line for these patches? Then at
> least some of them can go into the Xen repository.
>
> -- Keir
>
> On 21/08/2009 17:02, "Matt Fioravante" <Matthew.Fioravante@xxxxxxxxxx>
> wrote:
>
> > We are using xen and vtpm at JHU APL for a project and ran into many
> > problems. I've had to develop several patches and workarounds and wanted
> > to contribute them back to the xen community.
> >
> > Here are a few patches that will make the xen vtpm system more stable
> > and allow you to have persistent vtpms. In other words you can reboot a
> > domU and it will come back up with the same vtpm instance and retain all
> > the keys and data you stored in it.
> >
> > Also included is a patch that ports vtpm to tpm_emulator-0.5.1. The new
> > emulator has a lot of bug fixes over the old 0.4 and is recommended if
> > you want a working vtpm implementation. This port is incomplete, so
> > please see the details on that patch before applying it.
> >
> > Some of these are actual bug fixes while others are hacks/workarounds.
> > Becuase of this, they have been broken into several patches to assist
> > the developers in choosing which they want to integrate. With these
> > patches we have been successfully able to use persistent vtpms for
> > signing certificates.
> >
> > All of these patches can be applied on top of each other in any order.
> > $ patch -p1 < patchfile
> >
> >
> > Finally, there are also some bugs in the xen hotplug system and the
> > vtpm_manager. Sometimes the manager can get into a corrupted state and
> > it will cease to work properly. Workarounds for some of the problems are
> > included at the end of this email.
> >
> >
> > ==============================
> > vtpm_manager-hash_error.patch
> > ==============================
> > There is a bug in the vtpm_manager that has to do with hashing and
> > saving the NVM memory files (vtpm_dm_%d.data). The file is not truncated
> > when it is written and this results in the hash becoming invalid because
> > of the extra bits at the end of the file.
> >
> > This patch adds O_TRUNC to the flags when opening the file.
> >
> > More details on this issue are in the bug report on bugzilla
> > http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1488
> >
> > ==============================
> > vtpm-uuid.patch
> > ==============================
> > Right now xen will create a new vtpm instance everytime you start up a
> > domU, even if you specify the instance parameter in your config file.
> > Each vtpm instance is then given a uuid and the vtpm.db file maps
> > instance numbers to uuid numbers.
> >
> > This patch is a hack that lets you explicitly set the uuid of your vtpm
> > instance. Everytime you boot up your domU now the vtpm will get that
> > uuid and thus it will always get the same vtpm instance number instead
> > of being generated a new one.
> >
> > So for example, in your config file you would do something like this
> > vtpm = [ 'backend=0,uuid=dcdb124b-9fed-4040-b149-dd2dfd8d094c' ]
> >
> > If you are using this patch then be sure to also use the hash_error
> > patch, otherwise you may see checksum failed messages when booting
> > your domain and the vtpm tries to read the NVM file. These 2 patches
> > were made separate because the first is a bug fix and this one is more
> > of a hack.
> >
> > ==============================
> > vtpm-0.4-persistence.patch
> > ==============================
> > This patch is only needed if you want to continue using
> > tpm_emulator-0.4. It is not necessary if you are going to use the
> > tpm_emulator-0.5.1 patch.
> >
> > This patch will add
> > #define TPM_STRONG_PERSISTENCE
> > which will make the tpm_emulator send a TPM_SaveState command after
> > every tpm command it executes. This is needed because some commands like
> > TPM_TakeOwnership do not send the TPM_SaveState command on their own.
> > The tpm_emulator will only request the manager to save its state when
> > this TPM command is sent.
> >
> > So in short without this patch, if you took ownership of your vtpm and
> > then rebooted the domU, the the change in state would not be saved and
> > your vtpm would come back unowned again.
> >
> > I imagine several other tpm commands would have this problem as well.
> >
> > ==============================
> > vtpm-0.5.1.patch
> > ==============================
> > This patch will port vtpm to use tpm_emulator-0.5.1
> > The newer version of the emulator contains several bug fixes, one that
> > we were seeing in our use of vtpm.
> >
> > This patch also defines TPM_STRONG_PERSISTENCE for the new emulator.
> >
> > A couple of important notes about this patch:
> > -This has only been tested on PVM domU's. In theory it should work for
> > HVM but I have not tried it at all and can guarantee nothing.
> > -All the relevant changes in tools/vtpm/vtpm.patch have been ported to
> > tpm_emulator-0.5.1.
> > -None of the changes in tpm_emulator.patch have been ported. In
> > particular this means the BUILD_EMULATOR option, which as I understand
> > lets you use the tpm_emulator in dom0 for a machine that does
> > not have a real hardware TPM does not work. This functionality should be
> > easy to add though because the new emulator already comes with a kernel
> > module interface.
> > -No considerations were made for the VTPM_MULTI_VM feature (which is
> > supposedly unfinished). This patch may or may not break any progress
> > made on that feature.
> >
> > ============================
> > vtpm_manager and xen hotplug workarounds
> > ============================
> > Here are some issues I've run into when trying to use vtpm. Note that in
> > my test cases we were only using vtpms in PVM domains.
> >
> > It might make sense to add these to a readme or something somewhere
> > until the hotplug issues are fixed.
> >
> > 1-Q) When I boot my domU with a vtpm for the first time I get
> > the following error message in the vtpm_managerd output
> > Loading NVM.
> > Sending LoadNVM command
> > ERROR[VTPM]: Failed to load NVM
> > .INFO[VTPM]: [VTPM Listener]: VTPM Listener waiting for messages.
> > Reading LoadNVM header
> > 1-A) This is ok. This message comes up when the vtpm non-volatile memory
> > file does not exist, which is normal when xen creates a new vtpm
> > instance.
> >
> > 2-Q) When I start vtpm_managerd it starts spamming output to the console
> > forever and gives the following error:
> > ERROR[VTPM]: [Hotplug Listener]: Hotplug Listener can't read from ipc.
> > Errono = 0. Aborting...
> > 2-A) Sometimes the hotplug scripts and the fifos they use to
> > communicate
> > get in a corrupted state. We need to clear all the fifos.
> > 1) First, stop all of the vms that have vtpms.
> > 2) Kill the vtpm_managerd
> > 3) Search for vtpm processes.
> > #ps -ef | grep vtpm
> > You may see processes that look like the following. If you do
> > not see any then skip ahead to the next step.
> > /bin/bash /etc/xen/scripts/vtpm add
> > dd skip=10 bs=1 count=4 if=/var/vtpm/fifos/to_console.fifo
> > /usr/bin/vtpmd
> > First, kill any of the dd processes, and then run ps again. Most if
> > not all of the /etx/xen/scripts/vtpm processes should have quit.
> > Kill any of the remaining scripts/vtpm and vtpmd processes.
> > Note that after killing some of of the "vtpm add" processes
> > new "vtpm remove" processes may get spawned which you will
> > also need to kill.
> > 4) Delete all of the fifos and socks
> > #rm /var/vtpm/fifos/*
> > #rm /var/vtpm/socks/*
> > 5) Remove the lock files if they exist
> > # rm -rf /var/run/xen-hotplug/vtpm*
> > 6) Now start up the vtpm_managerd again, it should start without errors.
> > 7) Finally, you should be able to boot up the vms again without any
> > problems.
> >
> > 3-Q) When I start a domU that has a vtpm it hangs in the
> > pause state and will not boot. If I wait long enough it will quit and
> > tell me that the Hotplug scripts are not working.
> > 3-A) This occurs when we have stale lock files that did not get removed
> > properly.
> > Perform the same set of steps in 2-A.
> >
>
>
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