Re: lapic & npt

[Gerd Hoffmann <kraxel@redhat.com>]

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Avi Kivity wrote:
> Gerd Hoffmann wrote:
>>   Hi,
>>
>> I've just noticed that xenner doesn't work for 64bit xen guest kernels
>> on my new shiny barcelona box.  The VM crashes when trying to access the
>> lapic.  lapic setup is done before idt setup, register dump looks like
>> init state, thus it most likely is a triple fault resetting the vcpu.
>> Turning off npt fixes it.
>>
>> xenner maps the lapic to ffff820000000000 (64bit guests) or fe900000
>> (32bit guests).  32bit works fine even with npt enabled.
>>
>> host kernel is fedora 9 with kvm-69 modules.
>>
>> ideas anyone?
> 
> Turn on logging in lapic.c.  See if something turns up.

It doesn't come that far according to kvmtrace.

> If not, the page tables are probably set up incorrectly, but in a way
> that kvm doesn't notice.

Dunno.  Tried kvmtrace and got the results attached without and with
NTP.  Cutted down to the important sequence, starting with the apic MSR
read.  After the msr access there are some page faults (some page table
pages are allocated and used to map the apic, thus likely triggering
shadow pt updates).  Then the apic access (id register).

With npt kvm doesn't see the apic access at all.  Also the TDP_FAULT
line looks fishy to me.  The "virt = ... " isn't a (guest) virtual address.

btw: the iowrite to 0x00ea is console output.

ideas anyone?
  Gerd

-- 
http://kraxel.fedorapeople.org/xenner/

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1673786946412 (+    6068)  VMEXIT        vcpu = 0x00000000  pid = 0x0000102d [ exitcode = 0x0000007c, rip = 0xffff8300 0000a1d2 ]
0 (+       0)  MSR_READ      vcpu = 0x00000000  pid = 0x0000102d [ MSR# = 0x0000001b, data = 0x00000000 fee00900 ]
1673786950748 (+    4336)  VMENTRY       vcpu = 0x00000000  pid = 0x0000102d
1673786957068 (+    6320)  VMEXIT        vcpu = 0x00000000  pid = 0x0000102d [ exitcode = 0x00000003, rip = 0xffff8300 00006ceb ]
0 (+       0)  CR_READ       vcpu = 0x00000000  pid = 0x0000102d [ CR# = 3, value = 0x00000000 017a3000 ]
1673786966522 (+    9454)  VMENTRY       vcpu = 0x00000000  pid = 0x0000102d
1673786973678 (+    7156)  VMEXIT        vcpu = 0x00000000  pid = 0x0000102d [ exitcode = 0x0000004e, rip = 0xffff8300 00004023 ]
0 (+       0)  PAGE_FAULT    vcpu = 0x00000000  pid = 0x0000102d [ errorcode = 0x00000002, virt = 0xffff8300 00048000 ]
1673787002404 (+   28726)  VMENTRY       vcpu = 0x00000000  pid = 0x0000102d
1673787034034 (+   31630)  VMEXIT        vcpu = 0x00000000  pid = 0x0000102d [ exitcode = 0x0000004e, rip = 0xffff8300 00004023 ]
0 (+       0)  PAGE_FAULT    vcpu = 0x00000000  pid = 0x0000102d [ errorcode = 0x00000002, virt = 0xffff8300 00049000 ]
1673787049388 (+   15354)  VMENTRY       vcpu = 0x00000000  pid = 0x0000102d
1673787080890 (+   31502)  VMEXIT        vcpu = 0x00000000  pid = 0x0000102d [ exitcode = 0x0000004e, rip = 0xffff8300 0000a1ef ]
0 (+       0)  PAGE_FAULT    vcpu = 0x00000000  pid = 0x0000102d [ errorcode = 0x00000000, virt = 0xffff8200 00000020 ]
0 (+       0)  APIC_ACCESS   vcpu = 0x00000000  pid = 0x0000102d [ offset = 0x00000020 ]
1673787096270 (+   15380)  VMENTRY       vcpu = 0x00000000  pid = 0x0000102d

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1834321779170 (+    6312)  VMEXIT        vcpu = 0x00000000  pid = 0x00001080 [ exitcode = 0x0000007c, rip = 0xffff8300 0000a1d2 ]
0 (+       0)  MSR_READ      vcpu = 0x00000000  pid = 0x00001080 [ MSR# = 0x0000001b, data = 0x00000000 fee00900 ]
1834321783872 (+    4702)  VMENTRY       vcpu = 0x00000000  pid = 0x00001080
1834321793790 (+    9918)  VMEXIT        vcpu = 0x00000000  pid = 0x00001080 [ exitcode = 0x00000400, rip = 0xffff8300 00004023 ]
0 (+       0)  TDP_FAULT     vcpu = 0x00000000  pid = 0x00001080 [ errorcode = 0x00000006, virt = 0x00000000 00048000 ]
1834321818582 (+   24792)  VMENTRY       vcpu = 0x00000000  pid = 0x00001080
1834321851480 (+   32898)  VMEXIT        vcpu = 0x00000000  pid = 0x00001080 [ exitcode = 0x00000400, rip = 0xffff8300 00004023 ]
0 (+       0)  TDP_FAULT     vcpu = 0x00000000  pid = 0x00001080 [ errorcode = 0x00000006, virt = 0x00000000 00049000 ]
1834321870858 (+   19378)  VMENTRY       vcpu = 0x00000000  pid = 0x00001080
1834321906650 (+   35792)  VMEXIT        vcpu = 0x00000000  pid = 0x00001080 [ exitcode = 0x00000400, rip = 0xffff8300 000053b1 ]
0 (+       0)  TDP_FAULT     vcpu = 0x00000000  pid = 0x00001080 [ errorcode = 0x00000004, virt = 0x00000000 0000d000 ]
1834321912818 (+    6168)  VMENTRY       vcpu = 0x00000000  pid = 0x00001080
1834321931382 (+   18564)  VMEXIT        vcpu = 0x00000000  pid = 0x00001080 [ exitcode = 0x0000007b, rip = 0xffff8300 0000b256 ]
0 (+       0)  IO_WRITE      vcpu = 0x00000000  pid = 0x00001080 [ port = 0x00ea, size = 1 ]
1834322090822 (+  159440)  VMENTRY       vcpu = 0x00000000  pid = 0x00001080