linux-kernel - Re: [PATCH 0/2] Fix boot hang issue on Ampere Emag server

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Message-ID: <Y9laZ1nx+MzFHvQx@zx2c4.com>
Date:   Tue, 31 Jan 2023 19:13:59 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Jia He <justin.he@....com>, Huacai Chen <chenhuacai@...nel.org>,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexandru Elisei <alexandru.elisei@....com>
Subject: Re: [PATCH 0/2] Fix boot hang issue on Ampere Emag server

Actually...

On Tue, Jan 31, 2023 at 07:03:12PM +0100, Jason A. Donenfeld wrote:
> On Tue, Jan 31, 2023 at 08:18:49AM +0100, Ard Biesheuvel wrote:
> > (cc Jason for awareness)
> > 
> > On Tue, 31 Jan 2023 at 05:04, Jia He <justin.he@....com> 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.
> > 
> 
> On my phone and with very limited connectivity for another 10 days, but
> I wonder if there's a later place we could move this block:
> 
>     if (efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))
>         execute_with_initialized_rng(&refresh_nv_rng_seed_nb);
> 
> Is there any additional initialization that happens after
> efisubsys_init() that we're maybe missing out on there?

>From Jia's dmesg:

[   14.209389][    C2] random: crng init done

So SetVariable isn't even being called until 14 seconds after boot. That
suggests there's something else wrong here. I wonder how it is that
efibootmgr works, but this does not... Hm?

Jason