Re: [libvirt PATCH 1/2] qemu: support kvm-poll-control performance hint

QEMU version 4.2 introduced a performance feature under commit d645e13287 ("kvm: i386: halt poll control MSR support"). This patch adds a new KVM feature 'poll-control' to set this performance hint for KVM guests. The feature is off by default. To enable this hint and have libvirt add "-cpu host,kvm-poll-control=on" to the QEMU command line, the following XML code needs to be added to the guest's domain description: <features> <kvm> <poll-control state='on'/> </kvm> </features> Signed-off-by: Tim Wiederhake <twiederh(a)redhat.com&gt; --- docs/formatdomain.rst | 14 ++++++++------ docs/schemas/domaincommon.rng | 5 +++++ src/conf/domain_conf.c | 4 ++++ src/conf/domain_conf.h | 1 + src/qemu/qemu_command.c | 5 +++++ 5 files changed, 23 insertions(+), 6 deletions(-) diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst index a6ab845f92..cd5d7aae56 100644 --- a/docs/formatdomain.rst +++ b/docs/formatdomain.rst @@ -1766,6 +1766,7 @@ Hypervisors may allow certain CPU / machine features to be toggled on/off. <kvm> <hidden state='on'/> <hint-dedicated state='on'/> + <poll-control='on'/> </kvm> <xen> <e820_host state='on'/> @@ -1848,12 +1849,13 @@ are: ``kvm`` Various features to change the behavior of the KVM hypervisor. - ============== ====================================================================== ======= ============================ - Feature Description Value Since - ============== ====================================================================== ======= ============================ - hidden Hide the KVM hypervisor from standard MSR based discovery on, off :since:`1.2.8 (QEMU 2.1.0)` - hint-dedicated Allows a guest to enable optimizations when running on dedicated vCPUs on, off :since:`5.7.0 (QEMU 2.12.0)` - ============== ====================================================================== ======= ============================ + ============== ============================================================================ ======= ============================ + Feature Description Value Since + ============== ============================================================================ ======= ============================ + hidden Hide the KVM hypervisor from standard MSR based discovery on, off :since:`1.2.8 (QEMU 2.1.0)` + hint-dedicated Allows a guest to enable optimizations when running on dedicated vCPUs on, off :since:`5.7.0 (QEMU 2.12.0)` + poll-control Decrease IO completion latency by introducing a grace period of busy waiting on, off :since:`6.11.0 (QEMU 4.2)` + ============== ============================================================================ ======= ============================