On 06/03/2013 09:34 PM, Konrad Rzeszutek Wilk wrote:
On Sun, Jun 02, 2013 at 12:56:24AM +0530, Raghavendra K T wrote:Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> 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 Signed-off-by: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx> Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> --- Documentation/virtual/kvm/cpuid.txt | 4 ++++ Documentation/virtual/kvm/hypercalls.txt | 13 +++++++++++++ 2 files changed, 17 insertions(+) diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 83afe65..654f43c 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 || 6 || 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 ea113b5..2a4da11 100644 --- a/Documentation/virtual/kvm/hypercalls.txt +++ b/Documentation/virtual/kvm/hypercalls.txt @@ -64,3 +64,16 @@ 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 of the vcpu to be wokenup.woken up.
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