From a2e199915725e666772dd077dbffbef154e58096 Mon Sep 17 00:00:00 2001 From: "Luis R. Rodriguez" Date: Fri, 13 Feb 2015 17:13:40 +1030 Subject: virtual: Documentation: simplify and generalize paravirt_ops.txt 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-devel@lists.xenproject.org Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Luis R. Rodriguez Signed-off-by: Rusty Russell --- Documentation/virtual/00-INDEX | 3 +++ Documentation/virtual/paravirt_ops.txt | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) create mode 100644 Documentation/virtual/paravirt_ops.txt (limited to 'Documentation/virtual') diff --git a/Documentation/virtual/00-INDEX b/Documentation/virtual/00-INDEX index e952d30bbf0f..af0d23968ee7 100644 --- a/Documentation/virtual/00-INDEX +++ b/Documentation/virtual/00-INDEX @@ -2,6 +2,9 @@ Virtualization support in the Linux kernel. 00-INDEX - this file. + +paravirt_ops.txt + - Describes the Linux kernel pv_ops to support different hypervisors kvm/ - Kernel Virtual Machine. See also http://linux-kvm.org uml/ diff --git a/Documentation/virtual/paravirt_ops.txt b/Documentation/virtual/paravirt_ops.txt new file mode 100644 index 000000000000..d4881c00e339 --- /dev/null +++ b/Documentation/virtual/paravirt_ops.txt @@ -0,0 +1,32 @@ +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-ops 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 of code paths in + them are very performance critical. -- cgit v1.2.3-70-g09d2