Re: [Xen-devel] [PATCH v2] hvm/svm: Implement Debug events

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

On Ma, 2018-03-20 at 10:49 -0600, Tamas K Lengyel wrote:
> On Tue, Mar 20, 2018 at 3:40 AM, Alexandru Isaila
> <aisaila@xxxxxxxxxxxxxxx> wrote:
> >
> > At this moment the Debug events for the AMD architecture are not
> > forwarded to the monitor layer.
> >
> > This patch adds the Debug event to the common capabilities, adds
> > the VMEXIT_ICEBP then forwards the event to the monitor layer.
> >
> > Chapter 2: SVM Processor and Platform Extensions: "Note: A vector 1
> > exception generated by the single byte INT1
> > instruction (also known as ICEBP) does not trigger the #DB
> > intercept. Software should use the dedicated ICEBP
> > intercept to intercept ICEBP"
> >
> > ---
> > Changes since V1:
> >         - Get inst_len from __get_instruction_length()
> >         - Updated __get_instruction_length() for the INSTR_ICEBP
> >           instruction
> >
> > Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
> > ---
> >  xen/arch/x86/hvm/svm/emulate.c        |  1 +
> >  xen/arch/x86/hvm/svm/svm.c            | 37
> > +++++++++++++++++++++++++----------
> >  xen/arch/x86/hvm/svm/vmcb.c           |  2 +-
> >  xen/include/asm-x86/hvm/svm/emulate.h |  1 +
> >  xen/include/asm-x86/monitor.h         |  4 ++--
> >  5 files changed, 32 insertions(+), 13 deletions(-)
> >
> > diff --git a/xen/arch/x86/hvm/svm/emulate.c
> > b/xen/arch/x86/hvm/svm/emulate.c
> > index e1a1581..172369e 100644
> > --- a/xen/arch/x86/hvm/svm/emulate.c
> > +++ b/xen/arch/x86/hvm/svm/emulate.c
> > @@ -80,6 +80,7 @@ static const struct {
> >      [INSTR_RDTSC]   = { X86EMUL_OPC(0x0f, 0x31) },
> >      [INSTR_RDMSR]   = { X86EMUL_OPC(0x0f, 0x32) },
> >      [INSTR_CPUID]   = { X86EMUL_OPC(0x0f, 0xa2) },
> > +    [INSTR_ICEBP]   = { X86EMUL_OPC(   0, 0xf1) },
> >  };
> >
> >  int __get_instruction_length_from_list(struct vcpu *v,
> > diff --git a/xen/arch/x86/hvm/svm/svm.c
> > b/xen/arch/x86/hvm/svm/svm.c
> > index c34f5b5..d4f2290 100644
> > --- a/xen/arch/x86/hvm/svm/svm.c
> > +++ b/xen/arch/x86/hvm/svm/svm.c
> > @@ -1109,7 +1109,8 @@ static void noreturn svm_do_resume(struct
> > vcpu *v)
> >  {
> >      struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
> >      bool debug_state = (v->domain->debugger_attached ||
> > -                        v->domain-
> > >arch.monitor.software_breakpoint_enabled);
> > +                        v->domain-
> > >arch.monitor.software_breakpoint_enabled ||
> > +                        v->domain-
> > >arch.monitor.debug_exception_enabled);
> Please explain the rationale why this is included under
> "debug_exception" and not "software_breakpoint".
>
> Thanks,
> Tamas
>
Hi Tamas,

I've included the icebp under the debug_exception only to have
consistency with the vmx side. I saw this behavior after running
the swint-emulation from xtf.

Regards,
Alex

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