Re: [Xen-devel] acpidump crashes on some machines

[Andre Przywara <andre.przywara@xxxxxxx>]

On 06/30/2012 04:19 AM, Konrad Rzeszutek Wilk wrote:

Konrad, David,

back on track for this issue. Thanks for your input, I could do some 
more debugging (see below for a refresh):
It seems like it affects only the first page of the 1:1 mapping. I 
didn't have an issues with the last PFN or the page behind it (which 
failed properly).
David, thanks for the hint with varying dom0_mem parameter. I thought I 
already checked this, but I did it once again and it turned out that it 
is only an issue if dom0_mem is smaller than the ACPI area, which 
generates a hole in the memory map. So we have (simplified)
* 1:1 mapping to 1 MB
* normal mapping till dom0_mem
* unmapped area till ACPI E820 area
* ACPI E820 1:1 mapping

As far as I could chase it down the 1:1 mapping itself looks OK, I 
couldn't find any off-by-one bugs here. So maybe it is code that later 
on invalidates areas between the normal guest mapping and the ACPI mem?
Hope that helps, I will also try to find more about this.

Thanks,
Andre.

> > > [  351.964914] ------------[ cut here ]------------
> > > [  351.964924] WARNING: at /src/linux-2.6/xentest/testxenmap.c:24
> > > acpitest_init+0x5e/0x1000 [testxenmap]()
> > > [  351.964926] Hardware name: empty
> > > [  351.964928] We get cfef0 instead of ffffffffffffffff!
> > Is cfef0 part of the 1-1 mapping and in ACPI? On my box I see this:
> >
> > # dmesg | head -30 | grep bc55
> > [    0.000000] 1-1 mapping on bc558->bc5ac
> > [    0.000000] Xen: [mem 0x0000000040200000-0x00000000bc557fff] usable
> > [    0.000000] Xen: [mem 0x00000000bc558000-0x00000000bc560fff] ACPI data
> >
> > So the E820 has it marked a ACPI data and sure enough I also see this:
> >
> > [    0.000000] ACPI: DSDT 00000000bc558168 079E1 (v02 INTEL  DQ67SW   00000016 
> > INTL 20051117)
> >
> > Let me see what I get with the little module.
> So:
> [    0.000000] 1-1 mapping on 9a->100
> [    0.000000] 1-1 mapping on 20000->20200
> [    0.000000] 1-1 mapping on 40000->40200
> [    0.000000] 1-1 mapping on bc558->bc5ac
> [    0.000000] 1-1 mapping on bc5b4->bc8c5
> [    0.000000] 1-1 mapping on bc8c6->bcb7c
> [    0.000000] 1-1 mapping on bcd00->100000
>
> > dmesg | grep ACPI: | head
> [    0.000000] ACPI: RSDP 00000000000f0450 00024 (v02  INTEL)
> [    0.000000] ACPI: XSDT 00000000bc558070 00064 (v01 INTEL  DQ67SW   01072009 
> AMI  00010013)
> [    0.000000] ACPI: FACP 00000000bc55fb50 000F4 (v04 INTEL  DQ67SW   01072009 
> AMI  00010013)
> [    0.000000] ACPI: DSDT 00000000bc558168 079E1 (v02 INTEL  DQ67SW   00000016 
> INTL 20051117)
> [    0.000000] ACPI: FACS 00000000bc8dbf80 00040
> [    0.000000] ACPI: APIC 00000000bc55fc48 00072 (v03 INTEL  DQ67SW   01072009 
> AMI  00010013)
> [    0.000000] ACPI: TCPA 00000000bc55fcc0 00032 (v02 INTEL  DQ67SW   00000001 
> MSFT 01000013)
> [    0.000000] ACPI: SSDT 00000000bc55fcf8 00102 (v01 INTEL  DQ67SW   00000001 
> MSFT 03000001)
> [    0.000000] ACPI: MCFG 00000000bc55fe00 0003C (v01 INTEL  DQ67SW   01072009 
> MSFT 00000097)
> [    0.000000] ACPI: HPET 00000000bc55fe40 00038 (v01 INTEL  DQ67SW   01072009 
> AMI. 00000004)
>
> 02:11:06 # 42 :~/
> > rmmod acpidump;insmod /acpidump.ko pfn=0xbc55e
> 02:11:15 # 43 :~/
> > rmmod acpidump;insmod /acpidump.ko pfn=0xbc559
> 02:11:26 # 44 :~/
> > rmmod acpidump;insmod /acpidump.ko pfn=0xbc558
> insmod: error inserting '/acpidump.ko': -1 Invalid parameters
>
> 2:16:37 # 8 :/data/
> > insmod /acpidump.ko pfn=0xbc5ac
> insmod: error inserting '/acpidump.ko': -1 Invalid parameters
>
> 02:16:45 # 10 :/data/
> > dmesg | grep p2m
> [  389.847683] raw p2m (bc558) gives us: ffffffffffffffff
> [  701.348502] raw p2m (bc5ac) gives us: ffffffffffffffff
>
> Huh? Looks like I can access the ACPI regions (bc559 had a bunch of stuff),
> but _not_ on the boundary PFNs.
>
> Plot thickens - but sadly I won't be able to do much until Thursday.
>
> I think the issue is somewhere in set_phys_range_identity. This
> loop:
>   767         for (pfn = pfn_s; pfn < pfn_e; pfn++)
>   768                 if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
>   769                         break;
>   770
>
> Probably needs pfn <= pfn_e. But that still does not explain
> why pfn_s is failing.
>
> Or maybe in the pfn_to_mfn machinary. It certainly has a lot of
> overrides in it. If you were to instrument any of those to print
> out more details on the offending PFNs that could help.


--
Andre Przywara
AMD-OSRC (Dresden)
Tel: x29712


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