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

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 06/24/2015 12:14 PM, Fanhenglong 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*

How are you using Xen in this case? Are you by any chance using the
vm_event system in a way that sends back an "emulate" vm_event response
from userspace?

You might want to look at x86_emulate() in
xen/arch/x86/x86_emulate/x86_emulate.c and see if (and how) fxsave is
being handled.


HTH,
Razvan

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