On Mon, 2021-04-26 at 21:56 +0200, Thore Sommer wrote:
> Dear Maintainers,
> 
> during my testing with OVMF and swtpm I found out that kernel
> versions newer than 5.8 don't show any information in 
> "/sys/kernel/security/tpm0/binary_bios_measurements" if swtpm
> emulates a TPM 2.0 device. The file is still created but is empty.
> The expected result would be that 
> "/sys/kernel/security/tpm0/binary_bios_measurements" contains the
> TPM event log. TPM 1.2 devices are not affected.

I don't confirm this.  I have Linux version 5.12.0-rc5+ installed and I
see the attached in my binary_bios_measurements (I've run it through
tpm2-eventlog so you can see the actual events).

> With the help of git bisect I found out that the breaking kernel
> commit is 85467f63a05c43364ba0b90d0c05bb89191543fa.
> Reverting this on top the 5.12 release restores the expected
> functionality.
> 
> Thanks to apalos and leiflindholm on the #edk2 IRC channel for
> helping me with that.
> 
> I don't know if this is a bug in OVMF or in the Linux kernel, because
> on a real device with a TPM 2.0 the output was as expected.
> 
> Tested with edk2-ovmf 202102, swtpm 0.5.2 and qemu 5.2.0 on Ubuntu
> 20.04.
> 
> If further information is needed to resolve this problem, I'd be
> happy to provide them.

What that commit did was to allow the event log to be provided by the
ACPI table if one existed rather than always defaulting to it being
provided by the EFI configuration table.  What I suspect has happened
from this:

> [    0.017358] ACPI: Reserving TPM2 table memory at [mem 
> 0x7eb77000-0x7eb7704b]

Is that somehow you've got an empty TPM2 table installed in ACPI but I
don't know how you've done this.  On my OVMF boot I'm using the direct
kernel command line and I have secure boot enabled but not activated,
which is why you only see PCRs 0-7 in the log.

James