[vbox-dev] detailed paths from vm i/o to host?

Achim Hasenmüller achim.hasenmueller at oracle.com
Thu Dec 9 00:44:02 PST 2010

>> I wonder if anyone can provide some detailed info as how guest i/o comes to the host emulation layer (user space). For example, how does "outb port_num, val" instruction travel from guest kernel to host user space on AMD64 with VT-x/AMD-V?
>> The reason I aksed is that I was wondering if performance would be further improved if moving some emulation layer from host user space to host kernel layer? that should at least saves two context switches.
>> KVM provides some callbacks, any similar api exists for VBox? 

We do a lot more in kernel context than KVM and we have been doing so for many years. Our virtual device architecture lets you specify which handlers run at which context and you can handle simpler and more frequent cases in kernel mode and even decide in kernel mode that you can't handle the call and forward it to user mode.


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