diff options
| author | Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> | 2013-08-26 12:48:36 +0400 |
|---|---|---|
| committer | Gleb Natapov <gleb@redhat.com> | 2013-08-26 13:47:49 +0400 |
| commit | 9bc6cbebfe006bcf0f83b10221cd4b893a130d10 (patch) | |
| tree | 957ba8780239c78fdea13ceb78327c3652a9303f /Documentation/virtual | |
| parent | 24d2166beb2f0be7dd29ab6a0841c27bd669eae9 (diff) | |
| download | linux-9bc6cbebfe006bcf0f83b10221cd4b893a130d10.tar.xz | |
Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock
KVM_HC_KICK_CPU hypercall added to wakeup halted vcpu in paravirtual spinlock
enabled guest.
KVM_FEATURE_PV_UNHALT enables guest to check whether pv spinlock can be enabled
in guest.
Thanks Vatsa for rewriting KVM_HC_KICK_CPU
Cc: Rob Landley <rob@landley.net>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Acked-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'Documentation/virtual')
| -rw-r--r-- | Documentation/virtual/kvm/cpuid.txt | 4 | ||||
| -rw-r--r-- | Documentation/virtual/kvm/hypercalls.txt | 14 |
2 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 83afe65d4966..22ff659bc0fb 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -43,6 +43,10 @@ KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs KVM_FEATURE_ASYNC_PF || 4 || async pf can be enabled by || || writing to msr 0x4b564d02 ------------------------------------------------------------------------------ +KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit + || || before enabling paravirtualized + || || spinlock support. +------------------------------------------------------------------------------ KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side || || per-cpu warps are expected in || || kvmclock. diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt index ea113b5d87a4..022198e389d7 100644 --- a/Documentation/virtual/kvm/hypercalls.txt +++ b/Documentation/virtual/kvm/hypercalls.txt @@ -64,3 +64,17 @@ Purpose: To enable communication between the hypervisor and guest there is a shared page that contains parts of supervisor visible register state. The guest can map this shared page to access its supervisor register through memory using this hypercall. + +5. KVM_HC_KICK_CPU +------------------------ +Architecture: x86 +Status: active +Purpose: Hypercall used to wakeup a vcpu from HLT state +Usage example : A vcpu of a paravirtualized guest that is busywaiting in guest +kernel mode for an event to occur (ex: a spinlock to become available) can +execute HLT instruction once it has busy-waited for more than a threshold +time-interval. Execution of HLT instruction would cause the hypervisor to put +the vcpu to sleep until occurence of an appropriate event. Another vcpu of the +same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall, +specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0) +is used in the hypercall for future use. |