Chapter 3. Understanding Shared Info Pages
When an operating system boots, one of the first things it typically does is query the firmware to find out a little about its surroundings. This includes things like the amount of RAM available, what peripherals are connected, and what the current time is.
A kernel booting in a Xen environment, however, does not have access to the real firmware. Instead, there must be another mechanism. Much of the required information is provided by shared memory pages. There are two of these: the first is mapped into the guest’s address space by the domain builder at guest boot time; the second must be explicitly mapped by the guest.
The shared info pages do not completely replace a BIOS. One of the main uses for ...
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