Re: [PATCH v6 4/4] qemu: support dirty ring feature

From: Hyman Huang(黄勇) <huangy81(a)chinatelecom.cn&gt; dirty ring feature was introduced in qemu-6.1, this patch add corresponding feature named 'dirty-ring', which enable dirty ring feature when starting vm. to enable the feature, libvirt add "-accel dirty-ring-size=xxx" to QEMU command line, the following XML needs to be added to the guest's domain description: <features> <kvm> <dirty-ring state='on' size='xxx'> </kvm> </features> if property "state=on" but property "size" not be configured, set default ring size with 4096. since dirty ring can only be enabled by specifying "-accel" option and do not support the legacy style, it seems that there's no other way to work around this, so we use "-accel" option to specify accelerator instead of "-machine" when building qemu commandline. details about the qemu "-accel" option: https://lore.kernel.org/qemu-devel/3aa73987-40e8-3619-0723-9f17f73850bd@r... Signed-off-by: Hyman Huang(黄勇) <huangy81(a)chinatelecom.cn&gt; --- docs/formatdomain.rst | 18 ++++++++++-------- docs/schemas/domaincommon.rng | 10 ++++++++++ src/qemu/qemu_command.c | 6 ++++++ 3 files changed, 26 insertions(+), 8 deletions(-) diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst index eb8c973cf1..ea69b61c70 100644 --- a/docs/formatdomain.rst +++ b/docs/formatdomain.rst @@ -1843,6 +1843,7 @@ Hypervisors may allow certain CPU / machine features to be toggled on/off. <hint-dedicated state='on'/> <poll-control state='on'/> <pv-ipi state='off'/> + <dirty-ring state='on' size='4096'/> </kvm> <xen> <e820_host state='on'/> @@ -1925,14 +1926,15 @@ 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)` - poll-control Decrease IO completion latency by introducing a grace period of busy waiting on, off :since:`6.10.0 (QEMU 4.2)` - pv-ipi Paravirtualized send IPIs on, off :since:`7.10.0 (QEMU 3.1)` - ============== ============================================================================ ======= ============================ + ============== ============================================================================ ====================================================== ============================ + 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:`6.10.0 (QEMU 4.2)` + pv-ipi Paravirtualized send IPIs on, off :since:`7.10.0 (QEMU 3.1)` + dirty-ring Enable dirty ring feature on, off; size - must be power of 2, range [1024,65536] :since:`7.10.0 (QEMU 6.1)` + ============== ============================================================================ ====================================================== ============================ ``xen`` Various features to change the behavior of the Xen hypervisor.

diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng index f01b7a6470..5f9fe3cc58 100644 --- a/docs/schemas/domaincommon.rng +++ b/docs/schemas/domaincommon.rng @@ -7212,6 +7212,16 @@ <ref name="featurestate"/> </element> </optional> + <optional> + <element name="dirty-ring"> + <ref name="featurestate"/> + <optional> + <attribute name="size"> + <data type="unsignedInt"/> + </attribute> + </optional> + </element> + </optional> </interleave> </element> </define>

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 145596d11a..863876bfae 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -7043,6 +7043,12 @@ qemuBuildAccelCommandLineKvmOptions(virCommand *cmd, g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER; virCommandAddArg(cmd, "-accel"); virBufferAddLit(&buf, "kvm"); + + if (def->features[VIR_DOMAIN_FEATURE_KVM] == VIR_TRISTATE_SWITCH_ON && + def->kvm_features[VIR_DOMAIN_KVM_DIRTY_RING] == VIR_TRISTATE_SWITCH_ON) { + virBufferAsprintf(&buf, ",dirty-ring-size=%d", def->dirty_ring_size); + } + virCommandAddArgBuffer(cmd, &buf); } }