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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jun 24, 2015 at 10:31:57AM +0100, Andrew Cooper wrote:
> On 24/06/15 10:25, Razvan Cojocaru wrote:
> > 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.
> 
> The fxsave instruction has no emulation implementation.
> 
> "0f ae 07" is "fxsave (%rdi)" which means that either introspection is
> active, or %rdi is a pointer into an MMIO region.
> 

So I think this is not a regression? (I'm now trying to identify
possible blockers for the release)

Wei.

> ~Andrew
> 
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