x86: KVM guest: paravirtualized clocksource

This is the guest part of kvm clock implementation
It does not do tsc-only timing, as tsc can have deltas
between cpus, and it did not seem worthy to me to keep
adjusting them.

We do use it, however, for fine-grained adjustment.

Other than that, time comes from the host.

[randy dunlap: add missing include]
[randy dunlap: disallow on Voyager or Visual WS]

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2fadf794483d..40cedc255eda 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -373,6 +373,17 @@ config VMI
 	  at the moment), by linking the kernel to a GPL-ed ROM module
 	  provided by the hypervisor.
 
+config KVM_CLOCK
+	bool "KVM paravirtualized clock"
+	select PARAVIRT
+	depends on !(X86_VISWS || X86_VOYAGER)
+	help
+	  Turning on this option will allow you to run a paravirtualized clock
+	  when running over the KVM hypervisor. Instead of relying on a PIT
+	  (or probably other) emulation by the underlying device model, the host
+	  provides the guest with timing infrastructure such as time of day, and
+	  system time
+
 source "arch/x86/lguest/Kconfig"
 
 config PARAVIRT