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- .. SPDX-License-Identifier: GPL-2.0
- ============
- Paravirt_ops
- ============
- Linux provides support for different hypervisor virtualization technologies.
- Historically, different binary kernels would be required in order to support
- different hypervisors; this restriction was removed with pv_ops.
- Linux pv_ops is a virtualization API which enables support for different
- hypervisors. It allows each hypervisor to override critical operations and
- allows a single kernel binary to run on all supported execution environments
- including native machine -- without any hypervisors.
- pv_ops provides a set of function pointers which represent operations
- corresponding to low-level critical instructions and high-level
- functionalities in various areas. pv_ops allows for optimizations at run
- time by enabling binary patching of the low-level critical operations
- at boot time.
- pv_ops operations are classified into three categories:
- - simple indirect call
- These operations correspond to high-level functionality where it is
- known that the overhead of indirect call isn't very important.
- - indirect call which allows optimization with binary patch
- Usually these operations correspond to low-level critical instructions. They
- are called frequently and are performance critical. The overhead is
- very important.
- - a set of macros for hand written assembly code
- Hand written assembly codes (.S files) also need paravirtualization
- because they include sensitive instructions or some code paths in
- them are very performance critical.
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