Hi Ard,
We've run into a buggy UEFI implementation on the Qualcomm Snapdragon
based Lenovo ThinkPad T14s where ExitBootServices() often fails.
One bootloader entry may fail to start almost consistently (once in a
while it may start), while a second entry may always work even when the
kernel, dtb and initramfs images are copies of the failing entry on the
same ESP.
This can be worked around by starting and exiting a UEFI shell from the
bootloader or by starting the bootloader manually via the Boot Menu
(F12) before starting the kernel.
Notably starting the kernel automatically from the shell startup.nsh
does not work, while calling the same script manually works.
Based on your comments to a similar report for an older Snapdragon based
Lenovo UEFI implementation [1], I discovered that allocating an event
before calling ExitBootServices() can make the call succeed. There is
often no need to actually signal the event group, but the event must
remain allocated (i.e. CloseEvent() must not be called).
(Raising TPL or disabling interrupts does not seem to help.)
Also with the event signalling, ExitBootServices() sometimes fails when
starting the kernel automatically from a shell startup.nsh, while
systemd-boot seems to always work. This was only observed after removing
some efi_printk() used during the experiments from the stub...
Something is obviously really broken here, but do you have any
suggestions about what could be the cause of this as further input to
Qualcomm (and Lenovo) as they try to fix this?
For completeness, the first call to ExitBootServices() often fails also
on the x1e80100 reference design (CRD), and Qualcomm appears to have
been the ones providing the current retry implementation:
fc07716ba803 ("efi/libstub: Introduce ExitBootServices helper")
as this was needed to prevent similar boot failures with older Qualcomm
UEFI fw.
Marc is also hitting something like this on the Qualcomm X1E devkit
(i.e. with firmware that should not have any modifications from Lenovo).
I'm attaching the patch that allows me to boot kernels on the T14s
below.
Johan
[1] https://bugzilla.kernel.org/show_bug.cgi?id=216375#c10
