[QNX hypervisor 2.2 user manual]6.3.1 factory page and control page

QNX Hypervisor Shared memory by using factory pages and control pages （Factory pages and Control Pages） Realization .

Factory and control pages are kept shmem Virtual machine register of virtual device （ Reference resources “Virtual registers (guest_shm.h)”）.Guest Drivers in can access guest-physical These registers in memory , And interact with it , It's like interacting with physical registers , Read and write at the specified offset .

The page size of factory and control pages is the same as QNX Hypervisor The kernel page is the same （4KB）.

One 、 Factory page

because qvm The process will be vm Create a factory page , You need to host Guest Of VM Of qvm Configuration contains shmem Virtual device . Typically , Every qvm The configuration file contains only one shmem Virtual device , So every VM There is only one factory page .

A factory page contains information about shared memory , This includes a control page that stores each shared memory area guest-physical Area of address . And the value of this area will be in Guest Create or attach （attach） Different shared memory areas change .

A factory page may be located in Guest Any location of unallocated memory that can be accessed . for example , Suppose no other memory has been allocated , If we assign 192MB Of memory （ stay qvm The configuration has ram 192M）, We can put the factory page outside of this assignment at at 0x10000000 (256 MB). At this address guest-physical Address , It is not the actual physical address in the hardware .shmem The virtual device will be VM Virtual factory page . And no other device will use this location .

When Guest An application in wants