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

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

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

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