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

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.

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?

Has the emulator by any chance just emulated setting CR4.PAE?

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