Commit | Line | Data |
---|---|---|
a2e19991 LR |
1 | Paravirt_ops |
2 | ============ | |
3 | ||
4 | Linux provides support for different hypervisor virtualization technologies. | |
5 | Historically different binary kernels would be required in order to support | |
6 | different hypervisors, this restriction was removed with pv_ops. | |
7 | Linux pv_ops is a virtualization API which enables support for different | |
8 | hypervisors. It allows each hypervisor to override critical operations and | |
9 | allows a single kernel binary to run on all supported execution environments | |
10 | including native machine -- without any hypervisors. | |
11 | ||
12 | pv_ops provides a set of function pointers which represent operations | |
13 | corresponding to low level critical instructions and high level | |
14 | functionalities in various areas. pv-ops allows for optimizations at run | |
15 | time by enabling binary patching of the low-ops critical operations | |
16 | at boot time. | |
17 | ||
18 | pv_ops operations are classified into three categories: | |
19 | ||
20 | - simple indirect call | |
21 | These operations correspond to high level functionality where it is | |
22 | known that the overhead of indirect call isn't very important. | |
23 | ||
24 | - indirect call which allows optimization with binary patch | |
25 | Usually these operations correspond to low level critical instructions. They | |
26 | are called frequently and are performance critical. The overhead is | |
27 | very important. | |
28 | ||
29 | - a set of macros for hand written assembly code | |
30 | Hand written assembly codes (.S files) also need paravirtualization | |
31 | because they include sensitive instructions or some of code paths in | |
32 | them are very performance critical. |