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Luke Nowakowski-Krijger8373bc42019-07-10 08:30:52 -07001.. SPDX-License-Identifier: GPL-2.0
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Luis R. Rodrigueza2e19992015-02-13 17:13:40 +10304Paravirt_ops
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7Linux provides support for different hypervisor virtualization technologies.
8Historically different binary kernels would be required in order to support
9different hypervisors, this restriction was removed with pv_ops.
10Linux pv_ops is a virtualization API which enables support for different
11hypervisors. It allows each hypervisor to override critical operations and
12allows a single kernel binary to run on all supported execution environments
13including native machine -- without any hypervisors.
14
15pv_ops provides a set of function pointers which represent operations
16corresponding to low level critical instructions and high level
17functionalities in various areas. pv-ops allows for optimizations at run
18time by enabling binary patching of the low-ops critical operations
19at boot time.
20
21pv_ops operations are classified into three categories:
22
23- simple indirect call
Luke Nowakowski-Krijger8373bc42019-07-10 08:30:52 -070024 These operations correspond to high level functionality where it is
25 known that the overhead of indirect call isn't very important.
Luis R. Rodrigueza2e19992015-02-13 17:13:40 +103026
27- indirect call which allows optimization with binary patch
Luke Nowakowski-Krijger8373bc42019-07-10 08:30:52 -070028 Usually these operations correspond to low level critical instructions. They
29 are called frequently and are performance critical. The overhead is
30 very important.
Luis R. Rodrigueza2e19992015-02-13 17:13:40 +103031
32- a set of macros for hand written assembly code
Luke Nowakowski-Krijger8373bc42019-07-10 08:30:52 -070033 Hand written assembly codes (.S files) also need paravirtualization
34 because they include sensitive instructions or some of code paths in
35 them are very performance critical.