Re: Hibernate resume bug around 3,18-rc2 - Full PAT support

[Juergen Gross]

On 21/11/15 12:49, Vassilis Virvilis wrote:
> On 11/20/2015 02:23 PM, Juergen Gross wrote:
>> On 20/11/15 11:04, vasvir@xxxxxxxxxxxxxxxxx wrote:
>>>> I've just found a potential issue: In case MTRR is disabled by the BIOS
>>>> the PAT register of the boot processor won't be restored after resume.
>>>>
>>>> Can you check whether pr_info("MTRR: Disabled\n") has been executed in
>>>> early boot? If yes, this might be a BIOS option.
>>>>
>>>
>>> I don't have access right now. I will test it later tonight (This is my
>>> home machine).
>>>
>>> Would $dmesg | grep -i mtrr suffice or I need to look for the mtrr
>>> somewere else e.g. /proc /sys etc?
>>
>> I think grepping for MTRR in dmesg should be enough.
> 
> kernel 4.3 +nopat also died on the 4th or the 5th hibernate on the
> familiar (see previously attached image) "Calling lapic..." place.
> 
> $dmesg | grep -i mtr for 4.3 kernel with notpat
> [    0.189113] calling  mtrr_if_init+0x0/0x5f @ 1
> [    0.189116] initcall mtrr_if_init+0x0/0x5f returned 0 after 0 usecs
> [    0.189222] pmd_set_huge: Cannot satisfy [mem 0xf8000000-0xf8200000]
> with a huge-page mapping due to MTRR override.
> [    0.189559] calling  mtrr_init_finialize+0x0/0x3a @ 1
> [    0.189560] initcall mtrr_init_finialize+0x0/0x3a returned 0 after 0
> usecs
> [    8.994140] mtrr: type mismatch for e0000000,10000000 old: write-back
> new: write-combining
> [    8.994154] Failed to add WC MTRR for
> [00000000e0000000-00000000efffffff]; performance may suffer.
> 
> $dmesg | grep -i mtr for 4.3 kernel with default pat enabled
> [    0.189368] calling  mtrr_if_init+0x0/0x5f @ 1
> [    0.189370] initcall mtrr_if_init+0x0/0x5f returned 0 after 0 usecs
> [    0.189478] pmd_set_huge: Cannot satisfy [mem 0xf8000000-0xf8200000]
> with a huge-page mapping due to MTRR override.
> [    0.189814] calling  mtrr_init_finialize+0x0/0x3a @ 1
> [    0.189815] initcall mtrr_init_finialize+0x0/0x3a returned 0 after 0
> usecs
> 
> 
> I also checked my BIOS. I found nothing about mtrr. My BIOS manual is
> ftp://europe.asrock.com/Manual/H97%20Pro4.pdf. Can you see any option
> about MTRR?

As the BIOS obviously isn't disabling MTRR I don't think we have
to go that route any longer.

> Question: If we assume your theory is correct about mtrr/pat, wouldn't
> lockup/hang reboot every time the system goes to hibernate/resume? Can
> this assumption explain why the first hibernation/resume cycles in rapid
> succession after system boot are working and the long ones fail somewhat
> more consistently?

Hmm, I'm really not sure. It would depend on the usage of non-standard
cache mode mappings. But as MTRR isn't disabled this theory won't apply
to your problem.

> Note: With PAT enabled the system boots up significantly faster.
> 
> In the weekend I will return to 3.18-rc2 and I will try to verify my
> bisection is correct. Double guessing your self is a terrible thing...

Thanks.

> I will also try with nopat and I will run dmesg | grep -i mtr and post
> results
> 
> Unless you have any other suggestions...

I think we have to find out where the kernel is really hanging. Do you
have any chance to trigger a NMI?

Looking into suspend/resume code I found a strange inconsistency for
the lapic handling:

lapic_suspend()
{
...
#ifdef CONFIG_X86_THERMAL_VECTOR
        if (maxlvt >= 5)
                apic_pm_state.apic_thmr = apic_read(APIC_LVTTHMR);
#endif
...
}

lapic_resume()
{
...
#if defined(CONFIG_X86_MCE_INTEL)
        if (maxlvt >= 5)
                apic_write(APIC_LVTTHMR, apic_pm_state.apic_thmr);
#endif
...
}

and comparing that to:

clear_local_APIC()
{
...
#ifdef CONFIG_X86_THERMAL_VECTOR
        if (maxlvt >= 5) {
                v = apic_read(APIC_LVTTHMR);
                apic_write(APIC_LVTTHMR, v | APIC_LVT_MASKED);
        }
#endif
#ifdef CONFIG_X86_MCE_INTEL
        if (maxlvt >= 6) {
                v = apic_read(APIC_LVTCMCI);
                if (!(v & APIC_LVT_MASKED))
                        apic_write(APIC_LVTCMCI, v | APIC_LVT_MASKED);
        }
#endif
...
}

I think it would be interesting to know your kernel config...


Juergen

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