From: "Luis R. Rodriguez"
The general documentation we have for pv_ops is currenty present
on the IA64 docs, but since this documentation covers IA64 xen
enablement and IA64 Xen support got ripped out a while ago
through commit d52eefb47 present since v3.14-rc1 lets just
simplify, generalize and move the pv_ops documentation to a
shared place.
Cc: Isaku Yamahata
Cc: Jeremy Fitzhardinge
Cc: Chris Wright
Cc: Alok Kataria
Cc: Rusty Russell
Cc: virtualization@lists.linux-foundation.org
Cc: Tony Luck
Cc: Fenghua Yu
Cc: Boris Ostrovsky
Cc: xen-de...@lists.xenproject.org
Cc: k...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
Signed-off-by: Luis R. Rodriguez
---
Documentation/ia64/paravirt_ops.txt| 137 -
Documentation/virtual/00-INDEX | 3 +
Documentation/virtual/paravirt_ops.txt | 32
MAINTAINERS| 2 +-
4 files changed, 36 insertions(+), 138 deletions(-)
delete mode 100644 Documentation/ia64/paravirt_ops.txt
create mode 100644 Documentation/virtual/paravirt_ops.txt
diff --git a/Documentation/ia64/paravirt_ops.txt
b/Documentation/ia64/paravirt_ops.txt
deleted file mode 100644
index 39ded02..000
--- a/Documentation/ia64/paravirt_ops.txt
+++ /dev/null
@@ -1,137 +0,0 @@
-Paravirt_ops on IA64
-
- 21 May 2008, Isaku Yamahata
-
-
-Introduction
-
-The aim of this documentation is to help with maintainability and/or to
-encourage people to use paravirt_ops/IA64.
-
-paravirt_ops (pv_ops in short) is a way for virtualization support of
-Linux kernel on x86. Several ways for virtualization support were
-proposed, paravirt_ops is the winner.
-On the other hand, now there are also several IA64 virtualization
-technologies like kvm/IA64, xen/IA64 and many other academic IA64
-hypervisors so that it is good to add generic virtualization
-infrastructure on Linux/IA64.
-
-
-What is paravirt_ops?
--
-It has been developed on x86 as virtualization support via API, not ABI.
-It allows each hypervisor to override operations which are important for
-hypervisors at API level. And it allows a single kernel binary to run on
-all supported execution environments including native machine.
-Essentially paravirt_ops is a set of function pointers which represent
-operations corresponding to low level sensitive instructions and high
-level functionalities in various area. But one significant difference
-from usual function pointer table is that it allows optimization with
-binary patch. It is because some of these operations are very
-performance sensitive and indirect call overhead is not negligible.
-With binary patch, indirect C function call can be transformed into
-direct C function call or in-place execution to eliminate the overhead.
-
-Thus, operations of paravirt_ops are classified into three categories.
-- simple indirect call
- These operations correspond to high level functionality so 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 instructions. They
- are called frequently and performance critical. So 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 of code paths in
- them are very performance critical.
-
-
-The relation to the IA64 machine vector
-Linux/IA64 has the IA64 machine vector functionality which allows the
-kernel to switch implementations (e.g. initialization, ipi, dma api...)
-depending on executing platform.
-We can replace some implementations very easily defining a new machine
-vector. Thus another approach for virtualization support would be
-enhancing the machine vector functionality.
-But paravirt_ops approach was taken because
-- virtualization support needs wider support than machine vector does.
- e.g. low level instruction paravirtualization. It must be
- initialized very early before platform detection.
-
-- virtualization support needs more functionality like binary patch.
- Probably the calling overhead might not be very large compared to the
- emulation overhead of virtualization. However in the native case, the
- overhead should be eliminated completely.
- A single kernel binary should run on each environment including native,
- and the overhead of paravirt_ops on native environment should be as
- small as possible.
-
-- for full virtualization technology, e.g. KVM/IA64 or
- Xen/IA64 HVM domain, the result would be
- (the emulated platform machine vector. probably dig) + (pv_ops).
- This means that the virtualization support layer should be under
- the machine vector layer.
-
-Possibly it might be better to move some function pointers from
-paravirt_ops to machine vector. I
