From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: [PATCH V13 4/4] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock Date: Mon, 26 Aug 2013 14:18:36 +0530 Message-ID: <1377506916-26946-5-git-send-email-raghavendra.kt@linux.vnet.ibm.com> References: <1377506916-26946-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1377506916-26946-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: mingo@redhat.com, hpa@zytor.com, x86@kernel.org, gleb@redhat.com, pbonzini@redhat.com Cc: jeremy@goop.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, peterz@infradead.org, riel@redhat.com, virtualization@lists.linux-foundation.org, andi@firstfloor.org, Raghavendra K T , habanero@linux.vnet.ibm.com, drjones@redhat.com, konrad.wilk@oracle.com, Srivatsa Vaddagiri , ouyang@cs.pitt.edu, avi.kivity@gmail.com, tglx@linutronix.de, chegu_vinod@hp.com, linux-kernel@vger.kernel.org, srivatsa.vaddagiri@gmail.com, Rob Landley , torvalds@linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org 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 Signed-off-by: Srivatsa Vaddagiri Signed-off-by: Raghavendra K T Acked-by: Gleb Natapov Acked-by: Ingo Molnar --- Documentation/virtual/kvm/cpuid.txt | 4 ++++ Documentation/virtual/kvm/hypercalls.txt | 14 ++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 83afe65..22ff659 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 ea113b5..022198e 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. -- 1.7.11.7