On Mon, 7 Nov 2022 at 08:40, Dave Young <dyoung@xxxxxxxxxx> wrote: > > On Mon, 7 Nov 2022 at 15:36, Dave Young <dyoung@xxxxxxxxxx> wrote: > > > > Hi Ard, > > > > On Mon, 7 Nov 2022 at 15:30, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > On Mon, 7 Nov 2022 at 07:55, Dave Young <dyoung@xxxxxxxxxx> wrote: > > > > > > > > Hi, > > > > > > > > On Sat, 5 Nov 2022 at 22:16, <ns@xxxxxxxx> wrote: > > > > > > > > > > On 2022-11-05 05:49, Dave Young wrote: > > > > > > Baoquan, thanks for cc me. > > > > > > > > > > > > On Sat, 5 Nov 2022 at 11:10, Baoquan He <bhe@xxxxxxxxxx> wrote: > > > > > >> > > > > > >> Add Dave to CC > > > > > >> > > > > > >> On 10/28/22 at 01:02pm, ns@xxxxxxxx wrote: > > > > > >> > Greetings, > > > > > >> > > > > > > >> > I've been hitting a bug on my Lenovo ThinkPad T480 where kexecing will > > > > > >> > cause EFI mode (if that's the right term for it) to be unconditionally > > > > > >> > disabled, even when not using the --noefi option to kexec. > > > > > >> > > > > > > >> > What I mean by "EFI mode" being disabled, more than just EFI runtime > > > > > >> > services, is that basically nothing about the system's EFI is visible > > > > > >> > post-kexec. Normally you have a message like this in dmesg when the > > > > > >> > system is booted in EFI mode: > > > > > >> > > > > > > >> > [ 0.000000] efi: EFI v2.70 by EDK II > > > > > >> > [ 0.000000] efi: SMBIOS=0x7f98a000 ACPI=0x7fb7e000 ACPI 2.0=0x7fb7e014 > > > > > >> > MEMATTR=0x7ec63018 > > > > > >> > (obviously not the real firmware of the machine I'm talking about, but I > > > > > >> > can also send that if it would be of any help) > > > > > >> > > > > > > >> > No such message pops up in my dmesg as a result of this bug, & this > > > > > >> > causes some fallout like being unable to find the system's DMI > > > > > >> > information: > > > > > >> > > > > > > >> > <6>[ 0.000000] DMI not present or invalid. > > > > > >> > > > > > > >> > The efivarfs module also fails to load with -ENODEV. > > > > > >> > > > > > > >> > I've tried also booting with efi=runtime explicitly but it doesn't > > > > > >> > change anything. The kernel still does not print the name of the EFI > > > > > >> > firmware, DMI is still missing, & efivarfs still fails to load. > > > > > >> > > > > > > >> > I've been using the kexec_load syscall for all these tests, if it's > > > > > >> > important. > > > > > >> > > > > > > >> > Also, to make it very clear, all this only ever happens post-kexec. When > > > > > >> > booting straight from UEFI (with the EFI stub), all the aforementioned > > > > > >> > stuff that fails works perfectly fine (i.e. name of firmware is printed, > > > > > >> > DMI is properly found, & efivarfs loads & mounts just fine). > > > > > >> > > > > > > >> > This is reproducible with a vanilla 6.1-rc2 kernel. I've been trying to > > > > > >> > bisect it, but it seems like it goes pretty far back. I've got vanilla > > > > > >> > mainline kernel builds dating back to 5.17 that have the exact same > > > > > >> > issue. It might be worth noting that during this testing, I made sure > > > > > >> > the version of the kernel being kexeced & the kernel kexecing were the > > > > > >> > same version. It may not have been a problem in older kernels, but that > > > > > >> > would be difficult to test for me (a pretty important driver for this > > > > > >> > machine was only merged during v5.17-rc4). So it may not have been a > > > > > >> > regression & just a hidden problem since time immemorial. > > > > > >> > > > > > > >> > I am willing to test any patches I may get to further debug or fix > > > > > >> > this issue, preferably based on the current state of torvalds/linux.git. > > > > > >> > I can build & test kernels quite a few times per day. > > > > > >> > > > > > > >> > I can also send any important materials (kernel config, dmesg, firmware > > > > > >> > information, so on & so forth) on request. I'll also just mention I'm > > > > > >> > using kexec-tools 2.0.24 upfront, if it matters. > > > > > > > > > > > > Can you check the efi runtime in sysfs: > > > > > > ls /sys/firmware/efi/runtime-map/ > > > > > > > > > > > > If nothing then maybe you did not enable CONFIG_EFI_RUNTIME_MAP=y, it > > > > > > is needed for kexec UEFI boot on x86_64. > > > > > > > > > > Oh my, it really is that simple. > > > > > > > > > > Indeed, enabling this in the pre-kexec kernel fixes it all up. I had > > > > > blindly disabled it in my quest to downsize the pre-kexec kernel to > > > > > reduce boot time (it only runs a bootloader). In hindsight, the firmware > > > > > drivers section is not really a good section to tweak on a whim. > > > > > > > > > > I'm terribly sorry to have taken your time to "fix" this "bug". But I > > > > > must ask, is there any reason why this is a visible config option, or at > > > > > least not gated behind CONFIG_EXPERT? drivers/firmware/efi/runtime-map.c > > > > > is pretty tiny, & considering it depends on CONFIG_KEXEC_CORE, one > > > > > probably wants to have kexec work properly if they can even enable it. > > > > > > > > Glad to know it works with the .config tweaking. I can not recall any > > > > reason for that though. > > > > > > > > Since it sits in the efi code path, let's see how Ard thinks about > > > > your proposal. > > > > > > > > > > I don't understand why EFI_RUNTIME_MAP should depend on KEXEC_CORE at > > > all: it is documented as a feature that can be enabled for debugging > > > as well, and kexec does not work as expected without it. > > > > Probably debugging only mentioned in text, but not been considered in > > the kconfig logic :( > > > > > > > > Should we just change it like this perhaps? > > > > > > --- a/drivers/firmware/efi/Kconfig > > > +++ b/drivers/firmware/efi/Kconfig > > > @@ -28,8 +28,8 @@ config EFI_VARS_PSTORE_DEFAULT_DISABLE > > > > > > config EFI_RUNTIME_MAP > > > bool "Export efi runtime maps to sysfs" > > > - depends on X86 && EFI && KEXEC_CORE > > > - default y > > > + depends on X86 && EFI > > > + default KEXEC_CORE > > > help > > > > > > and maybe add an 'if EXPERT' so that the option is only visible to > > > modify when CONFIG_EXPERT=y ? > > > > Above changes look good to me. > > > > > > > > In any case, I intend to move this code into arch/x86 as well, so I'll > > > have a couple of patches out shortly. > > > > That would be better since it is X86 only. Thanks, Ard. > > Hmm, before doing that, do you think it is useful for debugging > purposes? That could be a reason to sit in efi code instead of x86 .. > This code was only ever enabled on x86, and on ARM/arm64, we can capture the memory map via efi=debug on any kernel build, and capture the virtual mappings using PTDUMP (which also gives us the exact attributes for each mapped region) So I don't think it has that much value on non-x86 tbh.
