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authorDavid Matlack <dmatlack@google.com>2020-04-17 15:14:46 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2020-04-24 12:53:17 -0400
commitacd05785e48c01edb2c4f4d014d28478b5f19fb5 (patch)
treec8a7003b579cbdc7c79d109ec563f84de7d07018 /Documentation/virt
parent87796555d48ca1cc681515e065b824ecab9c4282 (diff)
kvm: add capability for halt polling
KVM_CAP_HALT_POLL is a per-VM capability that lets userspace control the halt-polling time, allowing halt-polling to be tuned or disabled on particular VMs. With dynamic halt-polling, a VM's VCPUs can poll from anywhere from [0, halt_poll_ns] on each halt. KVM_CAP_HALT_POLL sets the upper limit on the poll time. Signed-off-by: David Matlack <dmatlack@google.com> Signed-off-by: Jon Cargille <jcargill@google.com> Reviewed-by: Jim Mattson <jmattson@google.com> Message-Id: <20200417221446.108733-1-jcargill@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt')
-rw-r--r--Documentation/virt/kvm/api.rst17
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index efbbe570aa9b..d871dacb984e 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5802,6 +5802,23 @@ If present, this capability can be enabled for a VM, meaning that KVM
will allow the transition to secure guest mode. Otherwise KVM will
veto the transition.
+7.20 KVM_CAP_HALT_POLL
+----------------------
+
+:Architectures: all
+:Target: VM
+:Parameters: args[0] is the maximum poll time in nanoseconds
+:Returns: 0 on success; -1 on error
+
+This capability overrides the kvm module parameter halt_poll_ns for the
+target VM.
+
+VCPU polling allows a VCPU to poll for wakeup events instead of immediately
+scheduling during guest halts. The maximum time a VCPU can spend polling is
+controlled by the kvm module parameter halt_poll_ns. This capability allows
+the maximum halt time to specified on a per-VM basis, effectively overriding
+the module parameter for the target VM.
+
8. Other capabilities.
======================