On 06/24/2015 12:31 PM, 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.
I see, these are the cases we wanted to treat with the old patch (I thick it was called "xen: Handle resumed instruction based on previous mem_event reply" - the early versions, with RFC) that sometimes bypassed the emulator in the introspection case. Without that, there's always going to be a potential current or future instruction not emulated, and then something like this happens. Cheers, Razvan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
