Re: [Xen-devel] (xen 4.6 unstable) triple fault when execute fxsave during the procedure of guest iso install

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.06.15 at 11:14, <fanhenglong@xxxxxxxxxx> wrote:
> I want to debug the procedure of windows os install with windbg,
> windbg executes instruction(fxsave) after the blank vm is started and before 
> guest iso start to install,
> 
> 
> fxsave trigger the following code path:
> vmx_vmexit_handler(EXIT_REASON_EPT_VIOLATION)
> ->ept_handle_violation
> ->hvm_hap_nested_page_fault
> ->handle_mmio_with_translation
> ->handle_mmio
> ->hvm_emulate_one
> ->x86_emulate
> 
> X86_emulate return X86EMUL_UNHANDLEABLE
> 
> The xl dmesg log;
> (d5) Writing SMBIOS tables ...
> (d5) Loading OVMF ...
> (XEN) d5v0 Over-allocation for domain 5: 2097409 > 2097408
> (XEN) memory.c:155:d5v0 Could not allocate order=0 extent: id=5 memflags=0 
> (0 of 1)
> (d5) Loading ACPI ...
> (d5) vm86 TSS at fc012d00
> (d5) BIOS map:
> (d5)  ffe00000-ffffffff: Main BIOS
> (d5) E820 table:
> (d5)  [00]: 00000000:00000000 - 00000000:000a0000: RAM
> (d5)  HOLE: 00000000:000a0000 - 00000000:000f0000
> (d5)  [01]: 00000000:000f0000 - 00000000:00100000: RESERVED
> (d5)  [02]: 00000000:00100000 - 00000000:f0000000: RAM
> (d5)  HOLE: 00000000:f0000000 - 00000000:fc000000
> (d5)  [03]: 00000000:fc000000 - 00000001:00000000: RESERVED
> (d5)  [04]: 00000001:00000000 - 00000002:0f6ed000: RAM
> (d5) Invoking OVMF ...
> (XEN) stdvga.c:147:d5v0 entering stdvga and caching modes
> (XEN) stdvga.c:151:d5v0 leaving stdvga
> (XEN) irq.c:276: Dom5 PCI link 0 changed 5 -> 11
> (XEN) irq.c:276: Dom5 PCI link 1 changed 10 -> 11
> (XEN) irq.c:276: Dom5 PCI link 2 changed 11 -> 10
> (XEN) irq.c:276: Dom5 PCI link 3 changed 5 -> 10
> (XEN) MMIO emulation failed: d5v0 64bit @ 0028:efe54dab -> 0f ae 07 fc ff 75 
> 10 48 8b 4d 08 48 89 e2 48 83
> (XEN) MMIO emulation failed: d5v0 64bit @ 0028:efe54dab -> 0f ae 07 fc ff 75 
> 10 48 8b 4d 08 48 89 e2 48 83
> (XEN) MMIO emulation failed: d5v0 64bit @ 0028:efe54dab -> 0f ae 07 fc ff 75 
> 10 48 8b 4d 08 48 89 e2 48 83
> (XEN) d5v0 Triple fault - invoking HVM shutdown action 1

Considering the address (below 4Gb) I'd view it equally possible
that it's OVMF that is running into this (and Windows may not
have got control at all by that time). But as others have said -
unless you're using VM events, it first of all would need to be
understood why fxsave would be issued on MMIO space, which
as a very minimum requires register state to be made visible.

Jan


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