Re: [kvm-devel] [RFC][PATCH 3/4] kvm-vmx: KVM_EXIT_DEBUG on #BP exceptions

[Jan Kiszka <jan.kiszka@web.de>]

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Avi Kivity wrote:
> Jan Kiszka wrote:
>> In order to allow the gdbstub of QEMU to push (soft) breakpoint handling
>> completely into the gdb frontend, this patch enables guest exits also
>> for #BP exceptions - in case guest debugging was turned on.
>>
>> Along this enhancement, this patch also fixes the flag manipulation for
>> the singlestep mode.
>>   
> 
> Suppose userspace determines the exception is due to a guest
> breakpoint.  How does it inject the debug exception?

Good question. Is there no "inject exception #XX" mechanism in kvm yet?

Will need this, as my current impression is that we better keep track of
breakpoints at qemu level to tell guest soft-BPs apart from host
injected ones. Would you suggest to add a separate IOCTL for exception
injection then? Or should the new guest debug IOCTL contain a flag that
signals "inject breakpoint trap" (both for guest soft-BP hits as well as
guests already in single step mode)?

Jan



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