Hello all,
I'm trying to add support for the firmware updates with the UEFI
capsule in
Qubes OS. I've got the troubles with reading ESRT (EFI System
Resource Table)
in the dom0, which is based on the EFI memory map. The EFI_MEMMAP
is not
enabled despite the loaded drivers (CONFIG_EFI, CONFIG_EFI_ESRT)
and kernel
cmdline parameters (add_efi_memmap):
```
[ 3.451249] efi: EFI_MEMMAP is not enabled.
```
The fwupd bases on the ESRT entries, which provide the system
firmware GUID.
The GUID is checked using LVFS metadata, which contains
information about updates.
When efi_memmap is not enabled, there are no ESRT entries in the
sysfs, and fwupd
has no information about the system firmware GUID. It is
therefore not possible to
check whether updates are available for the BIOS.
This is how the ESRT entries looks in the Ubuntu:
```
ubuntu@ubuntu:/sys/firmware/efi/esrt$ ll
total 0
drwxr-xr-x 3 root root 0 Jul 27 13:14 ./
drwxr-xr-x 6 root root 0 Jul 27 13:13 ../
drwxr-xr-x 3 root root 0 Jul 27 13:17 entries/
-r-------- 1 root root 4096 Jul 27 13:17 fw_resource_count
-r-------- 1 root root 4096 Jul 27 13:17 fw_resource_count_max
-r-------- 1 root root 4096 Jul 27 13:17 fw_resource_version
ubuntu@ubuntu:/sys/firmware/efi/esrt/entries/entry0$ ll
total 0
drwxr-xr-x 2 root root 0 Jul 27 13:17 ./
drwxr-xr-x 3 root root 0 Jul 27 13:17 ../
-r-------- 1 root root 4096 Jul 27 13:17 capsule_flags
-r-------- 1 root root 4096 Jul 27 13:17 fw_class
-r-------- 1 root root 4096 Jul 27 13:17 fw_type
-r-------- 1 root root 4096 Jul 27 13:17 fw_version
-r-------- 1 root root 4096 Jul 27 13:17 last_attempt_status
-r-------- 1 root root 4096 Jul 27 13:17 last_attempt_version
-r-------- 1 root root 4096 Jul 27 13:17
lowest_supported_fw_version
ubuntu@ubuntu:/sys/firmware/efi/esrt/entries/entry0$ sudo cat
fw_class
34578c72-11dc-4378-bc7f-b643866f598c
```
This is the source code of the ESRT driver, which provides those
directories:
https://gitlab.com/cki-project/kernel-ark/-/blob/os-build/drivers/firmware/efi/esrt.c
EFI_MEMMAP dependency is in the 248th line:
https://gitlab.com/cki-project/kernel-ark/-/blob/os-build/drivers/firmware/efi/esrt.c#L248
I need to pass ESRT to the dom0. What would be the best way to do that?
Ps. Marek Marczykowski-Górecki (Qubes Project lead) found some more information,
where the problem lays:
EFI_MEMMAP is not enabled on EFI_PARAVIRT (which I believe is the case on Xen dom0):
My reading the source code says the
Xen side to extract this info exists, but
Linux doesn't use it specifically, EFI config table address is
get here:
https://github.com/torvalds/linux/blob/master/arch/x86/xen/efi.c#L56-L63
But then nothing uses
efi_systab_xen.tables.
efi_config_parse_tables() function should be called on those
addresses:
https://github.com/torvalds/linux/blob/master/drivers/firmware/efi/efi.c#L542
But I don't think it is called in PV dom0 boot path (not fully sure about that yet).
Best Regards,
Norbert Kamiński
Junior Embedded Systems Engineer
GPG key ID: 9E9F90AFE10F466A
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