On Tue, 17 Feb 2026 at 18:27, Ard Biesheuvel <[email protected]> wrote: > > > > On Tue, 17 Feb 2026, at 11:01, Dave Young wrote: > > On Tue, 17 Feb 2026 at 17:20, Ard Biesheuvel <[email protected]> wrote: > >> > >> > >> On Tue, 17 Feb 2026, at 09:19, Dave Young wrote: > >> > Hi Ard, > >> > > >> > On Tue, 17 Feb 2026 at 16:10, Ard Biesheuvel <[email protected]> wrote: > >> >> > >> >> Hi Dave, > >> >> > >> >> On Tue, 17 Feb 2026, at 09:04, Dave Young wrote: > >> >> > Kernel panic occurs during a kexec reboot when EFI runtime services > >> >> > are not enabled in the first kernel. The issue is that the second > >> >> > kernel cannot find the ACPI RSDP address during boot. > >> >> > > >> >> > In legacy boot, the acpi_rsdp_addr is set in early x86 boot code. > >> >> > However, kernel decompression has moved to the EFI stub for EFI boot. > >> >> > Therefore, the x86 EFI stub must also be updated to store the > >> >> > acpi_rsdp_addr in the boot parameters to ensure the kexec kernel > >> >> > can find it. > >> >> > > >> >> > (Note: If the pre-kexec kernel was itself a kexec boot, the later > >> >> > kexec > >> >> > reboot will still utilize the legacy decompressor path, so the > >> >> > original > >> >> > code remains functional though some cleanups can be done later.) > >> >> > > >> >> > Signed-off-by: Dave Young <[email protected]> > >> >> > --- > >> >> > drivers/firmware/efi/libstub/x86-stub.c | 18 ++++++++++++++++++ > >> >> > 1 file changed, 18 insertions(+) > >> >> > > >> >> > >> >> If this issue is kexec-specific, can we move this to where the kexec > >> >> code prepares the boot_params struct for the next kernel? > >> >> > >> > > >> > The kexec use case is it depends on the pre-kexec kernel saving it > >> > during boot for noefi case. I do not have a better idea to do it in > >> > kexec code for the time being. > >> > >> How about something like this? > > > > Thanks! It works for me, however the legacy kexec_load syscall still > > failed with a panic I did not dig into the root cause yet, I supposed > > it will find the rsdp from /sys/firmware/efi/systab file, maybe some > > userspace code bug. > > > > Anyway I'm fine with this fix, would you like to send a formal patch > > since you proposed it? Otherwise I will resend with the changes. > > > > Excellent. I'll queue it with a link to this thread. >
Thanks a lot! Dave
