* Stefan Berger (stef...@linux.vnet.ibm.com) wrote: > On 03/21/2018 02:42 PM, Dr. David Alan Gilbert wrote: > > * Stefan Berger (stef...@linux.vnet.ibm.com) wrote: > > > Extend the docs related to TPM with specs related to VM save and > > > restore and a troubleshooting guide for TPM migration. > > > > > > Signed-off-by: Stefan Berger <stef...@linux.vnet.ibm.com> > > This seems ok, so: > > > > Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > > > > but comments below: > > > > > --- > > > docs/specs/tpm.txt | 106 > > > +++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 106 insertions(+) > > > > > > diff --git a/docs/specs/tpm.txt b/docs/specs/tpm.txt > > > index d1d7157..c230c4c 100644 > > > --- a/docs/specs/tpm.txt > > > +++ b/docs/specs/tpm.txt > > > @@ -200,3 +200,109 @@ crw-------. 1 root root 10, 224 Jul 11 10:11 > > > /dev/tpm0 > > > PCR-00: 35 4E 3B CE 23 9F 38 59 ... > > > ... > > > PCR-23: 00 00 00 00 00 00 00 00 ... > > > + > > > + > > > +=== Migration with the TPM emulator === > > > + > > > +The TPM emulator supports the following types of virtual machine > > > migration: > > > + > > > +- VM save / restore (migration into a file) > > > +- Network migration > > > +- Snapshotting (migration into storage like QoW2 or QED) > > > + > > > +The following command sequences can be used to test VM save / restore. > > > + > > > + > > > +In a 1st terminal start an instance of a swtpm using the following > > > command: > > > + > > > +mkdir /tmp/mytpm1 > > > +swtpm socket --tpmstate dir=/tmp/mytpm1 \ > > > + --ctrl type=unixio,path=/tmp/mytpm1/swtpm-sock \ > > > + --log level=20 --tpm2 > > > + > > > +In a 2nd terminal start the VM: > > > + > > > +qemu-system-x86_64 -display sdl -enable-kvm \ > > > + -m 1024 -boot d -bios bios-256k.bin -boot menu=on \ > > > + -chardev socket,id=chrtpm,path=/tmp/mytpm1/swtpm-sock \ > > > + -tpmdev emulator,id=tpm0,chardev=chrtpm \ > > > + -device tpm-tis,tpmdev=tpm0 \ > > > + -monitor stdio \ > > > + test.img > > > + > > > +Verify that the attached TPM is working as expected using applications > > > inside > > > +the VM. > > > + > > > +To store the state of the VM use the following command in the QEMU > > > monitor in > > > +the 2nd terminal: > > > + > > > +(qemu) migrate "exec:cat > testvm.bin" > > > +(qemu) quit > > > + > > > +At this point a file called 'testvm.bin' should exists and the swtpm and > > > QEMU > > > +processes should have ended. > > > + > > > +To test 'VM restore' you have to start the swtpm with the same parameters > > > +as before. If previously a TPM 2 [--tpm2] was saved, --tpm2 must now be > > > +passed again on the command line. > > > + > > > +In the 1st terminal restart the swtpm with the same command line as > > > before: > > > + > > > +swtpm socket --tpmstate dir=/tmp/mytpm1 \ > > > + --ctrl type=unixio,path=/tmp/mytpm1/swtpm-sock \ > > > + --log level=20 --tpm2 > > > + > > > +In the 2nd terminal restore the state of the VM using the additonal > > > +'-incoming' option. > > > + > > > +qemu-system-x86_64 -display sdl -enable-kvm \ > > > + -m 1024 -boot d -bios bios-256k.bin -boot menu=on \ > > > + -chardev socket,id=chrtpm,path=/tmp/mytpm1/swtpm-sock \ > > > + -tpmdev emulator,id=tpm0,chardev=chrtpm \ > > > + -device tpm-tis,tpmdev=tpm0 \ > > > + -incoming "exec:cat < testvm.bin" \ > > > + test.img > > > + > > > + > > > +Troubleshooting migration: > > > + > > > +There are several reasons why migration may fail. In case of problems, > > > +please ensure that the command lines adhere to the following rules and, > > > +if possible, that identical versions of QEMU and swtpm are used at all > > > +times. > > > + > > > +VM save and restore: > > > + - QEMU command line parameters should be identical apart from the > > > + '-incoming' option on VM restore > > > + - swtpm command line parameters should be identical > > > + > > > +VM migration to 'localhost': > > > + - QEMU command line parameters should be identical apart from the > > > + '-incoming' option on the destination side > > > + - swtpm command line parameters should point to two different > > > + directories on the source and destination swtpm (--tpmstate dir=...) > > > + (especially if different versions of libtpms were to be used on the > > > + same machine). > > > + > > > +VM migration across the network: > > > + - QEMU command line parameters should be identical apart from the > > > + '-incoming' option on the destination side > > > + - swtpm command line parameters should be identical > > > + > > > +VM Snapshotting: > > > + - QEMU command line parameters should be identical > > Well, they don't actually need to be identical; they just need to be > > identically configured as far as the state goes. For example all the > > paths to storage can be completely different on the two QEMUs. > > There is some leeway here in the parameters. For troubleshooting purposes it > may be the easiest to keep parameters the same and then slowly adjust them > to where one wants to have them. I don't want to go there , though. > > > > + - swtpm command line parameters should be identical > > > + > > > + > > > +Besides that, migration failure reasons on the swtpm level may include > > > +the following: > > > + > > > + - the versions of the swtpm on the source and destination sides are > > > + incompatible > > > + - downgrading of TPM state may not be supported > > > + - the source and destination libtpms were compiled with different > > > + compile-time options and the destination side refuses to accept the > > > + state > > > + - different migration keys are used on the source and destination side > > > + and the destination side cannot decrypt the migrated state > > > + (swtpm ... --migration-key ... ) > > Are there particular error messages swtpm will produce in these cases > > to make it easy for people to tell which has happened? > > There are some error messages that libtpms will write if for example the > checksum of the state was incorrect: > > Volatile state checksum error: 0x83 > > Generally, the error code will also propagate back to this part in QEMU and > at least that error code will be display with the message indicating the > type of blob that was not accepted: > > "tpm-emulator: Setting the stateblob (type %d) failed with a TPM error 0x%x", > type, tpm_result > > > The tpm_result may be one of several error codes that could occur, like a > hash was tried to be set that the implementation does not support, which > would result in error code 0x83 (TPM_RC_HASH), or an RSA scheme is used by > the imported blob that is not supported, which would result in error code > 0x84 (TPM_RC_VALUE). There are many more. The question is what would one do > with the additional knowledge of the error code. Under normal circumstances > these error conditions wouldn't be encountered, unless someone deliberately > resumed a VM after having compiled libtpms with a 'non-standard' set of > compile-time options...
OK, that's fine; although when we find out the mistakes people make in practice, it might be a good place to put the explanations of what not to do! Dave > Stefan > > > > > > Dave > > > > > -- > > > 2.5.5 > > > > > -- > > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK > > > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
