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Message-Id: <20120423100034.30893.81866.sendpatchset@codeblue.in.ibm.com>
Date: Mon, 23 Apr 2012 15:30:34 +0530
From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To: Jeremy Fitzhardinge <jeremy@...p.org>,
Greg Kroah-Hartman <gregkh@...e.de>,
Alexander Graf <agraf@...e.de>,
Randy Dunlap <rdunlap@...otime.net>, linux-doc@...r.kernel.org,
"H. Peter Anvin" <hpa@...or.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
KVM <kvm@...r.kernel.org>,
Stefano Stabellini <stefano.stabellini@...citrix.com>,
Virtualization <virtualization@...ts.linux-foundation.org>,
X86 <x86@...nel.org>, Gleb Natapov <gleb@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
Avi Kivity <avi@...hat.com>,
LKML <linux-kernel@...r.kernel.org>
Cc: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
Xen <xen-devel@...ts.xensource.com>,
Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
Sasha Levin <levinsasha928@...il.com>
Subject: [PATCH RFC V6 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock
From: Raghavendra K T <raghavendra.kt@...ux.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. support in host is queried via
ioctl(KVM_CHECK_EXTENSION, KVM_CAP_PV_UNHALT)
Thanks Alex for KVM_HC_FEATURES inputs and Vatsa for rewriting KVM_HC_KICK_CPU
Signed-off-by: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
---
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 6386f8c..7e2eba0 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1119,6 +1119,13 @@ 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_PV_UNHALT)
+
+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..062dff9 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_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
new file mode 100644
index 0000000..c9e8b9c
--- /dev/null
+++ b/Documentation/virtual/kvm/hypercalls.txt
@@ -0,0 +1,59 @@
+KVM Hypercalls Documentation
+===========================
+Template for documentation is
+The documenenation for hypercalls should inlcude
+1. Hypercall name, value.
+2. Architecture(s)
+3. status (deprecated, obsolete, active)
+4. Purpose
+
+
+1. KVM_HC_VAPIC_POLL_IRQ
+------------------------
+value: 1
+Architecture: x86
+Purpose:
+
+2. KVM_HC_MMU_OP
+------------------------
+value: 2
+Architecture: x86
+status: deprecated.
+Purpose: Support MMU operations such as writing to PTE,
+flushing TLB, release PT.
+
+3. KVM_HC_FEATURES
+------------------------
+value: 3
+Architecture: PPC
+Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
+used to enumerate which hypercalls are available. On PPC, either device tree
+based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration
+mechanism (which is this hypercall) can be used.
+
+4. KVM_HC_PPC_MAP_MAGIC_PAGE
+------------------------
+value: 4
+Architecture: PPC
+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
+------------------------
+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 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.
--
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