linux-kernel - Re: [GIT pull] x86/urgent for 5.3-rc5

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Date:   Sun, 25 Aug 2019 21:32:18 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Pu Wen <puwen@...on.cn>, Thomas Gleixner <tglx@...utronix.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [GIT pull] x86/urgent for 5.3-rc5

On Sun, Aug 25, 2019 at 11:38:50AM -0700, Linus Torvalds wrote:
> On Sun, Aug 25, 2019 at 11:29 AM Borislav Petkov <bp@...e.de> wrote:
> >
> > My lazy, sticky Sunday brain could come up only with this:
> 
> Looks reasonable, except I think this only runs at boot, right?
> 
> I _think_ the boot CPU is magical during suspend/resume, and doesn't
> do the full CPU bringup.
> 
> Although I guess this would still report it for the other CPU's? I
> didn't check if this gets done during CPU bringup of secondary CPU's.

So after adding a dump_stack() at the beginning of this function (yap,
I'm lazy) I see during boot:

[    0.230044] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.3.0-rc5+ #9
[    0.230759] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-1 04/01/2014
[    0.231690] Call Trace:
[    0.232097]  dump_stack+0x46/0x60
[    0.232496]  x86_init_rdrand+0xf/0xa1
[    0.232496]  identify_cpu+0x352/0x540
[    0.232496]  identify_boot_cpu+0xc/0x8f
[    0.232496]  check_bugs+0x28/0x8e4
[    0.232496]  ? __get_locked_pte+0x13e/0x1f0
[    0.232496]  start_kernel+0x4ae/0x4ca

and also on all the remaining 15 CPUs of the guest. Then, suspending to
RAM and resuming right afterwards says:

[   51.620230] Disabling non-boot CPUs ...
[   51.622745] smpboot: CPU 1 is now offline
[   51.627264] smpboot: CPU 2 is now offline
[   51.630581] smpboot: CPU 3 is now offline
[   51.634533] smpboot: CPU 4 is now offline
[   51.638715] smpboot: CPU 5 is now offline
[   51.642590] smpboot: CPU 6 is now offline
[   51.645890] smpboot: CPU 7 is now offline
[   51.649076] smpboot: CPU 8 is now offline
[   51.652362] smpboot: CPU 9 is now offline
[   51.655647] smpboot: CPU 10 is now offline
[   51.659061] smpboot: CPU 11 is now offline
[   51.662772] smpboot: CPU 12 is now offline
[   51.665863] smpboot: CPU 13 is now offline
[   51.667980] smpboot: CPU 14 is now offline
[   51.671644] smpboot: CPU 15 is now offline
[   51.675640] ACPI: Low-level resume complete
[   51.675640] PM: Restoring platform NVS memory
[   51.675640] Enabling non-boot CPUs ...
[   51.728674] x86: Booting SMP configuration:
[   51.729015] smpboot: Booting Node 0 Processor 1 APIC 0x1
[   51.625362] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.3.0-rc5+ #9
[   51.625362] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-1 04/01/2014
[   51.625362] Call Trace:
[   51.625362]  dump_stack+0x46/0x60
[   51.625362]  x86_init_rdrand+0xf/0xa1
[   51.625362]  identify_cpu+0x352/0x540
[   51.625362]  identify_secondary_cpu+0x13/0x80
[   51.625362]  smp_store_cpu_info+0x45/0x50
[   51.625362]  start_secondary+0x4f/0x180
[   51.625362]  secondary_startup_64+0xa4/0xb0
[   51.740833] CPU1 is up
...

and the remaining 14(!). Yes, this doesn't run on the BSP during resume.
I think the better thing to do would be to stick this in a CPUHP
notifier...

Btw:

Subject: Undelivered Mail Returned to Sender

...

<puwen@...on.cn>: Host or domain name not found. Name service error for
    name=spam01.hygon.cn type=AAAA: Host found but no data record of requested
    type

hygon.cn domain doesn't even resolve from here. Oh boy.

-- 
Regards/Gruss,
    Boris.

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