Re: [Xen-devel] [PATCH] x86/monitor: Notify monitor if an emulation fails.

[Petre Ovidiu PIRCALABU <ppircalabu@xxxxxxxxxxxxxxx>]

On Lu, 2017-07-10 at 12:30 -0600, Tamas K Lengyel wrote:
> On Mon, Jul 10, 2017 at 11:07 AM, Petre Pircalabu
> <ppircalabu@xxxxxxxxxxxxxxx> wrote:
> >
> > If case of a vm_event with the emulate_flags set, if the
> > instruction
> > cannot be emulated, the monitor should be notified instead of
> > directly
> > injecting a hw exception.
> > This behavior can be used to re-execute an instruction not
> > supported by
> > the emulator using the real processor (e.g. altp2m) instead of just
> > crashing.
> >
> > Signed-off-by: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
> > ---
> >  tools/libxc/include/xenctrl.h     |  2 ++
> >  tools/libxc/xc_monitor.c          | 14 ++++++++++++++
> >  xen/arch/x86/hvm/emulate.c        |  5 ++++-
> >  xen/arch/x86/hvm/monitor.c        | 19 +++++++++++++++++++
> >  xen/arch/x86/monitor.c            | 12 ++++++++++++
> >  xen/include/asm-x86/domain.h      |  1 +
> >  xen/include/asm-x86/hvm/monitor.h |  1 +
> >  xen/include/asm-x86/monitor.h     |  3 ++-
> >  xen/include/public/domctl.h       |  1 +
> >  xen/include/public/vm_event.h     |  2 ++
> >  10 files changed, 58 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/libxc/include/xenctrl.h
> > b/tools/libxc/include/xenctrl.h
> > index c51bb3b..8deb5ac 100644
> > --- a/tools/libxc/include/xenctrl.h
> > +++ b/tools/libxc/include/xenctrl.h
> > @@ -2029,6 +2029,8 @@ int xc_monitor_debug_exceptions(xc_interface
> > *xch, domid_t domain_id,
> >  int xc_monitor_cpuid(xc_interface *xch, domid_t domain_id, bool
> > enable);
> >  int xc_monitor_privileged_call(xc_interface *xch, domid_t
> > domain_id,
> >                                 bool enable);
> > +int xc_monitor_emul_unhandleable(xc_interface *xch, domid_t
> > domain_id,
> > +                                 bool enable);
> >  /**
> >   * This function enables / disables emulation for each REP for a
> >   * REP-compatible instruction.
> > diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
> > index b44ce93..8e72c6c 100644
> > --- a/tools/libxc/xc_monitor.c
> > +++ b/tools/libxc/xc_monitor.c
> > @@ -216,6 +216,20 @@ int xc_monitor_privileged_call(xc_interface
> > *xch, domid_t domain_id,
> >      return do_domctl(xch, &domctl);
> >  }
> >
> > +int xc_monitor_emul_unhandleable(xc_interface *xch, domid_t
> > domain_id,
> > +                                 bool enable)
> > +{
> > +    DECLARE_DOMCTL;
> > +
> > +    domctl.cmd = XEN_DOMCTL_monitor_op;
> > +    domctl.domain = domain_id;
> > +    domctl.u.monitor_op.op = enable ? XEN_DOMCTL_MONITOR_OP_ENABLE
> > +                                    :
> > XEN_DOMCTL_MONITOR_OP_DISABLE;
> > +    domctl.u.monitor_op.event =
> > XEN_DOMCTL_MONITOR_EVENT_EMUL_UNHANDLEABLE;
> > +
> > +    return do_domctl(xch, &domctl);
> > +}
> > +
> >  /*
> >   * Local variables:
> >   * mode: C
> > diff --git a/xen/arch/x86/hvm/emulate.c
> > b/xen/arch/x86/hvm/emulate.c
> > index e97aa69..083a38a 100644
> > --- a/xen/arch/x86/hvm/emulate.c
> > +++ b/xen/arch/x86/hvm/emulate.c
> > @@ -14,12 +14,14 @@
> >  #include <xen/sched.h>
> >  #include <xen/paging.h>
> >  #include <xen/trace.h>
> > +#include <xen/vm_event.h>
> >  #include <asm/event.h>
> >  #include <asm/i387.h>
> >  #include <asm/xstate.h>
> >  #include <asm/hvm/emulate.h>
> >  #include <asm/hvm/hvm.h>
> >  #include <asm/hvm/ioreq.h>
> > +#include <asm/hvm/monitor.h>
> >  #include <asm/hvm/trace.h>
> >  #include <asm/hvm/support.h>
> >  #include <asm/hvm/svm/svm.h>
> > @@ -2101,7 +2103,8 @@ void hvm_emulate_one_vm_event(enum emul_kind
> > kind, unsigned int trapnr,
> >          return;
> >      case X86EMUL_UNHANDLEABLE:
> >          hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event",
> > &ctx);
> > -        hvm_inject_hw_exception(trapnr, errcode);
> > +        if ( (kind != EMUL_KIND_NORMAL) ||
> > !hvm_monitor_emul_unhandleable() )
> Why is there this check for !EMUL_KIND_NORMAL?
>
> Tamas
>
> ________________________
> This email was scanned by Bitdefender

Hi Tamas,

I have checked with Razvan and this condition is no longer necessary.
I will remove it and send a v2.

Many thanks,
Petre

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