RE: [PATCH 0/2] Fix boot hang issue on Ampere Emag server

[Justin He]

Hi Jason

> -----Original Message-----
> From: Jason A. Donenfeld <Jason@xxxxxxxxx>
> Sent: Wednesday, February 1, 2023 2:23 AM
> To: Justin He <Justin.He@xxxxxxx>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>; Huacai Chen <chenhuacai@xxxxxxxxxx>;
> linux-efi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Alexandru Elisei
> <Alexandru.Elisei@xxxxxxx>
> Subject: Re: [PATCH 0/2] Fix boot hang issue on Ampere Emag server
>
> On Tue, Jan 31, 2023 at 03:21:39PM +0000, Justin He wrote:
> > Hi Ard,
> >
> > > -----Original Message-----
> > > From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > > Sent: Tuesday, January 31, 2023 3:19 PM
> > > To: Justin He <Justin.He@xxxxxxx>; Jason A. Donenfeld
> > > <Jason@xxxxxxxxx>
> > > Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>; linux-efi@xxxxxxxxxxxxxxx;
> > > linux-kernel@xxxxxxxxxxxxxxx; Alexandru Elisei
> > > <Alexandru.Elisei@xxxxxxx>
> > > Subject: Re: [PATCH 0/2] Fix boot hang issue on Ampere Emag server
> > >
> > > (cc Jason for awareness)
> > >
> > > On Tue, 31 Jan 2023 at 05:04, Jia He <justin.he@xxxxxxx> wrote:
> > > >
> > > > I met a hung task warning and then kernel was hung forever with
> > > > latest kernel on an Ampere Emag server.
> > > >
> > > > The root cause is kernel was hung  when invoking an efi rts call
> > > > to set the RandomSeed variable during the booting stage. The
> > > > arch_efi_call_virt call (set_variable) was never returned and then
> > > > caused the
> > > hung task error.
> > > >
> > >
> > > Given that EFI variables work on this platform (as far as I know),
> > > the problem may be that we are calling SetVariable() too early.
> > >
> > > Could you double check whether setting variables works as expected?
> > > You can use efibootmgr -t 10 as root (for example) to set the boot
> > > timeout, and check whether the new value is retained after a reboot
> > > (efibootmgr will print the current value for you)
> > >
> > > Could you also please share the kernel log up until the point where it
> hangs?
> > >
> > The set_variable seems to be ok in 5.19+:
> > root@:~# efibootmgr -t 10
> > BootCurrent: 0000
> > Timeout: 10 seconds
>
> I think what we want to learn is whether efibootmgr -t 10 works in the latest
> RC. If not, it would suggest the issue isn't with the seed setting, but with some
> other unrelated change.
>
> Can you run efibootmgr -t 10 (or whatever) again on a kernel where you've
> commented out these lines in efi.c inside of efisubsys_init():
>
>     if (efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))
>         execute_with_initialized_rng(&refresh_nv_rng_seed_nb);
>
> -->
>
>     // if (efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))
>     //     execute_with_initialized_rng(&refresh_nv_rng_seed_nb);
>
As your suggested (comment above execute_with_initialized_rng in latest kernel):
The efibootmgr -t X will be hung. Looks like one certain commit before your patch
broke the set_variable efi call. I will dig into the further debug and tell you the result.

---
Cheers,
Justin.
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