Re: [PATCH v3 3/5] schema: add TPM emulator <source type='file' path='..'>

Hi On Fri, Oct 11, 2024 at 5:49 PM Stefan Berger <stefanb(a)linux.ibm.com&gt; wrote: > > > > On 10/4/24 9:32 AM, marcandre.lureau(a)redhat.com wrote: >> From: Marc-André Lureau <marcandre.lureau(a)redhat.com&gt; >> >> Learn to parse a file path for the TPM state. >> >> Signed-off-by: Marc-André Lureau <marcandre.lureau(a)redhat.com&gt; >> --- >> docs/formatdomain.rst | 19 ++++++++++++++ >> src/conf/domain_conf.c | 28 +++++++++++++++++++++ >> src/conf/domain_conf.h | 9 +++++++ >> src/conf/schemas/domaincommon.rng | 14 +++++++++++ >> tests/qemuxmlconfdata/tpm-emulator-tpm2.xml | 1 + >> 5 files changed, 71 insertions(+) >> >> diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst >> index 4336cff3ac..992bb98730 100644 >> --- a/docs/formatdomain.rst >> +++ b/docs/formatdomain.rst >> @@ -8173,6 +8173,25 @@ Example: usage of the TPM Emulator >> The default version used depends on the combination of hypervisor, guest >> architecture, TPM model and backend. >> >> +``source`` >> + The ``source`` element specifies the location of the TPM state storage . This >> + element only works with the ``emulator`` backend. >> + >> + If not specified, the storage configuration is left to libvirt discretion. >> + >> + This element requires that swtpm v0.7 or later is installed. >> + >> + The following attributes are supported: >> + >> + ``type`` >> + The type of storage. It's possible to provide "file" to utilize a single >> + file or block device where the TPM state will be stored. >> + >> + ``path`` >> + The path to the TPM state storage. > > The file backend of swtpm does not do the locking similar to what the > dir backend does because those who added the file backend didn't > need/want it. If we now give full control to the path of the TPM state > file to the user via the domain XML then whose fault is it if two VMs > use the same path to a file backend and stomp on the TPM state file? Is > it the fault of the user because of how he defined the path in the XMLs? Imho, it's desirable to have a similar locking behaviour regardless of the backend and prevent users for mistakenly using the same file.