Public bug reported:
On noble with 6.17.0-1017-azure-fde (amd64, source package linux-azure-
fde-6.17), /boot/config-$(uname -r) has "# CONFIG_DMI_SYSFS is not set",
so /sys/firmware/dmi/entries does not exist, and installing linux-
modules-extra-$(uname -r) does not provide dmi-sysfs. Only the root-only
/sys/firmware/dmi/tables/DMI is available.
The setting comes from the linux-azure annotations, so it affects every
amd64 Azure flavour (azure and azure-fde, including the HWE backports)
in every series:
CONFIG_DMI_SYSFS policy<{'amd64': 'n', 'arm64': 'm'}>
It is listed under "Annotations without notes", and it is the same in
the linux-azure trees for noble, questing and resolute (6.19.0-1001).
The main linux kernel has 'm' on all architectures (resolute and
unstable).
Hyper-V does expose SMBIOS memory devices (type 17), and the entries are
readable when the module is present.
Use case: TDX attestation tooling on Azure confidential VMs, for example
https://github.com/easy-tee/attest, reads the per-entry SMBIOS memory
devices from /sys/firmware/dmi/entries/17-*/raw to report the VM's
memory size (https://github.com/easy-
tee/attest/blob/c17eca07bfd55539805dda2bb1add4cf0b32df12/crates/measure/src/platform.rs#L75-L96).
On this kernel, attestation evidence generation fails with "No such file
or directory".
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2045561 moved dmi-
sysfs.ko from linux-modules-extra into linux-modules for the main
kernels (jammy, mantic, noble), noting the module doesn't depend on
firmware. Please build it as a module on amd64 Azure kernels as well,
and ship it in linux-modules.
** Affects: linux-azure (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2172766
Title:
linux-azure: please enable CONFIG_DMI_SYSFS=m on amd64 (all Azure
flavours, including azure-fde)
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