Re: [Xen-devel] Failed vm entry with heavy use of emulator

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/01/16 13:39, Razvan Cojocaru wrote:
> On 01/05/2016 01:56 PM, Andrew Cooper wrote:
>> On 05/01/16 11:49, Tamas K Lengyel wrote:
>>> Hi all,
>>> I've been stress-testing the built-in emulator using the vm_event
>>> response VM_EVENT_FLAG_EMULATE feature. In the test I've turned all
>>> pages non-readable by default and all trapped instructions to be
>>> emulated. My test code can be found at
>>> <https://github.com/tklengyel/xen/compare/read_emul?expand=1>https://github.com/tklengyel/xen/compare/read_emul?expand=1.
>>>
>>> The following crash is reproducible and has been verified by Razvan as
>>> well.
>>>
>>> (XEN) p2m.c:1726:d1v0 calling mem_access_emulate_one, kind 0
>>> (XEN) Failed vm entry (exit reason 0x80000021) caused by invalid guest
>>> state (0).
>>> (XEN) ************* VMCS Area **************
>>> (XEN) *** Guest State ***
>>> (XEN) CR0: actual=0x000000008001003b, shadow=0x000000008001003b,
>>> gh_mask=ffffffffffffffff
>>> (XEN) CR4: actual=0x00000000000426f9, shadow=0x00000000000406f9,
>>> gh_mask=ffffffffffffffff
>>> (XEN) CR3 = 0x0000000000185000
>>> (XEN) PDPTE0 = 0x0000000000186001  PDPTE1 = 0x0000000000187001
>>> (XEN) PDPTE2 = 0x0000000000188001  PDPTE3 = 0x0000000000189001
>>> (XEN) RSP = 0x000000008276dc28 (0x000000008276dc28)  RIP =
>>> 0x00000000826bce1c (0x00000000826bce1c)
>>> (XEN) RFLAGS=0x00000002 (0x00000002)  DR7 = 0x0000000000000400
>>> (XEN) Sysenter RSP=000000008078b000 CS:RIP=0008:00000000826830c0
>>> (XEN)        sel  attr  limit   base
>>> (XEN)   CS: 0008 0c09b ffffffff 0000000000000000
>>> (XEN)   DS: 0023 0c0f3 ffffffff 0000000000000000
>>> (XEN)   SS: 0010 0c093 ffffffff 0000000000000000
>>> (XEN)   ES: 0023 0c0f3 ffffffff 0000000000000000
>>> (XEN)   FS: 0030 04093 00003748 0000000082770c00
>>> (XEN)   GS: 0000 1c000 ffffffff 0000000000000000
>>> (XEN) GDTR:            000003ff 0000000080b95000
>>> (XEN) LDTR: 0000 1c000 ffffffff 0000000000000000
>>> (XEN) IDTR:            000007ff 0000000080b95400
>>> (XEN)   TR: 0028 0008b 000020ab 00000000801da000
>>> (XEN) EFER = 0x0000000000000000  PAT = 0x0007010600070106
>>> (XEN) PreemptionTimer = 0x00000000  SM Base = 0x00000000
>>> (XEN) DebugCtl = 0x0000000000000000  DebugExceptions = 0x0000000000000000
>>> (XEN) Interruptibility = 00000000  ActivityState = 00000000
>>> (XEN) *** Host State ***
>>> (XEN) RIP = 0xffff82d0802075c0 (vmx_asm_vmexit_handler)  RSP =
>>> 0xffff830430d97f90
>>> (XEN) CS=e008 SS=0000 DS=0000 ES=0000 FS=0000 GS=0000 TR=e040
>>> (XEN) FSBase=0000000000000000 GSBase=0000000000000000
>>> TRBase=ffff830430d9bc00
>>> (XEN) GDTBase=ffff830430d8c000 IDTBase=ffff830430d98000
>>> (XEN) CR0=000000008005003b CR3=00000004136d0000 CR4=00000000000426e0
>>> (XEN) Sysenter RSP=ffff830430d97fc0 CS:RIP=e008:ffff82d08024db30
>>> (XEN) EFER = 0x0000000000000000  PAT = 0x0000050100070406
>>> (XEN) *** Control State ***
>>> (XEN) PinBased=0000003f CPUBased=b6a075fa SecondaryExec=000000eb
>>> (XEN) EntryControls=000051ff ExitControls=000fefff
>>> (XEN) ExceptionBitmap=00060042 PFECmask=00000000 PFECmatch=00000000
>>> (XEN) VMEntry: intr_info=800000d1 errcode=00000000 ilen=00000000
>>> (XEN) VMExit: intr_info=00000000 errcode=00000000 ilen=00000003
>>> (XEN)         reason=80000021 qualification=0000000000000000
>>> (XEN) IDTVectoring: info=800000d1 errcode=00000000
>>> (XEN) TSC Offset = 0x0000004ed9c86354
>>> (XEN) TPR Threshold = 0x00  PostedIntrVec = 0x00
>>> (XEN) EPT pointer = 0x000000041124e01e  EPTP index = 0x0000
>>> (XEN) Virtual processor ID = 0x0011 VMfunc controls = 0000000000000000
>>> (XEN) **************************************
>>> (XEN) domain_crash called from vmx.c:2761
>>>
>>> Any tips on how to further debug this issue?
>> Do you have a log of the instructions emulated?
> Here's a quick log of the emulated instructions on my setup:
> http://pastebin.com/raw/XXQ0Lnzh

Hmm - according to that, the final instruction emulated was

d1v0 32bit @ 0008:828925db -> fa

which is the 'cli' instruction.

I would start there - I doubt it is an instruction which is emulated often.

~Andrew

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