[Xen-devel] How Xen handles Dom1 interrupts?

["Jun Koi" <junkoi2004@xxxxxxxxx>]

Good morning,

I am new to Xen, and trying to understand how Xen works. I have some
questions about virtualization of interrupts on Xen. Thanks in advance
for all helps.

1) From papers about Xen architecture found at Xen homepage, Xen
seemingly intercepts interrupts of Dom1 (paravirtualization). So
interrupts occur in Dom1's context are sent to Xen, and Xen handles
them. Is that correct?

But then how can Dom1 gets the interrupts? For example if int3 occurs
inside Dom1, Xen intercepts int3, but then how debugger (like gdb) can
still work in Dom1? Maybe Xen sends that interrupt back to Dom1 after
processing it in VMM layer?

2) I have read
linux-xen-sparse/arch/i386/kernel/{traps-xen.c,traps.c,vmlinux.lds.S},
and looks like Dom1 still handles interrupts itself? Why, because I
suppose that the VMM already intercepts those interrupts?

3) How is linux-xen-sparse/arch/i386/kernel/traps-xen.c compiled,
while it is not refereed to in
linux-xen-sparse/arch/i386/kernel/Makefile? I see traps.c is refereed
instead of traps-xen.c, but I still saw traps-xen.o there after
compiling? What traps.c does, and what traps-xen.c does, since both
are very similar to me.



Thanks.
Jun

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