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SubjectRe: [PATCH RFC V9 18/19] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock
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@linux.vnet.ibm.com>
>>
>> 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@linux.vnet.ibm.com>
>> Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
>> ---
>> 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.

Yep. :)



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