From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: [PATCH RFC V4 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock Date: Sat, 14 Jan 2012 23:57:11 +0530 Message-ID: <20120114182710.8604.22277.sendpatchset__18819.3562011749$1326565706$gmane$org@oc5400248562.ibm.com> References: <20120114182501.8604.68416.sendpatchset@oc5400248562.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120114182501.8604.68416.sendpatchset@oc5400248562.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: Jeremy Fitzhardinge , Randy Dunlap , linux-doc@vger.kernel.org, KVM , Konrad Rzeszutek Wilk , Glauber Costa , Jan Kiszka , Rik van Riel , Dave Jiang , "H. Peter Anvin" , Thomas Gleixner , Rob Landley , X86 , Gleb Natapov , Avi Kivity , Alexander Graf , Stefano Stabellini , Paul Mackerras , Sedat Dilek , Ingo Molnar , LKML , Greg Kroah-Hartman , Virtualization , Marcelo Tosatti Cc: Peter Zijlstra , Raghavendra K T , Srivatsa Vaddagiri , Dave Hansen , Suzuki Poulose , Sasha Levin List-Id: virtualization@lists.linuxfoundation.org Add Documentation on CPUID, KVM_CAP_PVLOCK_KICK, and Hypercalls supported. KVM_HC_KICK_CPU hypercall added to wakeup halted vcpu in paravirtual spinlock enabled guest. KVM_FEATURE_PVLOCK_KICK enables guest to check whether pv spinlock can be enabled in guest. support in host is queried via ioctl(KVM_CHECK_EXTENSION, KVM_CAP_PVLOCK_KICK) A minimal Documentation and template is added for hypercalls. Signed-off-by: Raghavendra K T Signed-off-by: Srivatsa Vaddagiri --- diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index e2a4b52..1583bc7 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -1109,6 +1109,13 @@ support. Instead it is reported via if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the feature in userspace, then you can enable the feature for KVM_SET_CPUID2. +Paravirtualized ticket spinlocks can be enabled in guest by checking whether +support exists in host via, + + ioctl(KVM_CHECK_EXTENSION, KVM_CAP_PVLOCK_KICK) + +if this call return true, guest can use the feature. + 4.47 KVM_PPC_GET_PVINFO Capability: KVM_CAP_PPC_GET_PVINFO diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 8820685..c7fc0da 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -39,6 +39,10 @@ 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_PVLOCK_KICK || 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 new file mode 100644 index 0000000..7872da5 --- /dev/null +++ b/Documentation/virtual/kvm/hypercalls.txt @@ -0,0 +1,54 @@ +KVM Hypercalls Documentation +=========================== +Template for documentation is +The documenenation for hypercalls should inlcude +1. Hypercall name, value. +2. Architecture(s) +3. Purpose + + +1. KVM_HC_VAPIC_POLL_IRQ +------------------------ +value: 1 +Architecture: x86 +Purpose: + +2. KVM_HC_MMU_OP +------------------------ +value: 2 +Architecture: x86 +Purpose: Support MMU operations such as writing to PTE, +flushing TLB, release PT. + +3. KVM_HC_FEATURES +------------------------ +value: 3 +Architecture: PPC +Purpose: + +4. KVM_HC_PPC_MAP_MAGIC_PAGE +------------------------ +value: 4 +Architecture: PPC +Purpose: To enable communication between the hypervisor and guest there is a +new shared page that contains parts of supervisor visible register state. +The guest can map this shared page using this hypercall. + +5. KVM_HC_KICK_CPU +------------------------ +value: 5 +Architecture: x86 +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 (unless yield_on_hlt=0) 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. + +TODO: +1. more information on input and output needed? +2. Add more detail to purpose of hypercalls.