Re: [Xen-devel] [PATCH v7 2/3] x86/vm_event: Add HVM debug exception vm_events

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.06.16 at 19:26, <tamas@xxxxxxxxxxxxx> wrote:
> On Tue, Jun 28, 2016 at 1:37 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>> On 27.06.16 at 20:08, <tamas@xxxxxxxxxxxxx> wrote:
>>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>>> @@ -3376,7 +3376,29 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
>>>              HVMTRACE_1D(TRAP_DEBUG, exit_qualification);
>>>              write_debugreg(6, exit_qualification | DR_STATUS_RESERVED_ONE);
>>>              if ( !v->domain->debugger_attached )
>>> -                vmx_propagate_intr(intr_info);
>>> +            {
>>> +                unsigned long insn_len = 0;
>>> +                int rc;
>>> +                unsigned long trap_type = MASK_EXTR(intr_info,
>>> +                                                    
> INTR_INFO_INTR_TYPE_MASK);
>>> +
>>> +                if ( trap_type >= X86_EVENTTYPE_SW_INTERRUPT )
>>> +                    __vmread(VM_EXIT_INSTRUCTION_LEN, &insn_len);
>>> +
>>> +                rc = hvm_monitor_debug(regs->eip,
>>> +                                       HVM_MONITOR_DEBUG_EXCEPTION,
>>> +                                       trap_type, insn_len);
>>> +
>>> +                /*
>>> +                 * !rc    continue normally
>>> +                 * rc > 0 paused waiting for response, work here is done
>>> +                 * rc < 0 error in monitor/vm_event, crash
>>> +                 */
>>> +                if ( !rc )
>>> +                    vmx_propagate_intr(intr_info);
>>> +                if ( rc < 0 )
>>> +                    goto exit_and_crash;
>>> +            }
>>
>> As opposed to earlier versions, here omitting the "else" seems
>> undesirable. Or, perhaps better, simply re-order the two if()-s.
>> This is to make clear that what is now the second if() does in no
>> way depend on what the body of the current first if() does.
>>
>> The same would then apply to patch 3, and I'd be fine doing the
>> adjustment while committing (provided all necessary acks trickle
>> in). Feel free to add my ack here for the few changes for which
>> that's actually relevant.
> 
> That sounds fine to me. I think this patch only needs Wei's or Ian's
> ack now for the libxc changes.

Indeed.

Jan


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