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authorLinus Torvalds <torvalds@linux-foundation.org>2015-02-18 20:24:01 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-18 20:24:01 +0300
commit53861af9a17022898619a2ae4ead0dfc601b7c13 (patch)
treedc11088d9e86fa1d8d8479974864153a8f976897 /Documentation/virtual
parent5c2770079fb9b8c5bfb7113d9e76de66e77a0e24 (diff)
parent5b40a7daf51812b35cf05d1601a779a7043f8414 (diff)
downloadlinux-53861af9a17022898619a2ae4ead0dfc601b7c13.tar.xz
Merge tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
Pull virtio updates from Rusty Russell: "OK, this has the big virtio 1.0 implementation, as specified by OASIS. On top of tht is the major rework of lguest, to use PCI and virtio 1.0, to double-check the implementation. Then comes the inevitable fixes and cleanups from that work" * tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (80 commits) virtio: don't set VIRTIO_CONFIG_S_DRIVER_OK twice. virtio_net: unconditionally define struct virtio_net_hdr_v1. tools/lguest: don't use legacy definitions for net device in example launcher. virtio: Don't expose legacy net features when VIRTIO_NET_NO_LEGACY defined. tools/lguest: use common error macros in the example launcher. tools/lguest: give virtqueues names for better error messages tools/lguest: more documentation and checking of virtio 1.0 compliance. lguest: don't look in console features to find emerg_wr. tools/lguest: don't start devices until DRIVER_OK status set. tools/lguest: handle indirect partway through chain. tools/lguest: insert driver references from the 1.0 spec (4.1 Virtio Over PCI) tools/lguest: insert device references from the 1.0 spec (4.1 Virtio Over PCI) tools/lguest: rename virtio_pci_cfg_cap field to match spec. tools/lguest: fix features_accepted logic in example launcher. tools/lguest: handle device reset correctly in example launcher. virtual: Documentation: simplify and generalize paravirt_ops.txt lguest: remove NOTIFY call and eventfd facility. lguest: remove NOTIFY facility from demonstration launcher. lguest: use the PCI console device's emerg_wr for early boot messages. lguest: always put console in PCI slot #1. ...
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/00-INDEX3
-rw-r--r--Documentation/virtual/paravirt_ops.txt32
2 files changed, 35 insertions, 0 deletions
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.