On Sat, Nov 20, 2021 at 03:20:48 -0500, huang...@chinatelecom.cn wrote:
> From: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
>
> 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/3aa73987-40e8-3619-0723-9f17f7385...@redhat.com/
>
> Signed-off-by: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
> ---
> 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.
Okay, so both hunks belong actually to the previous commit.
> 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>
And this one too.
> 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);
> }
> }
A test case is needed both for qemuxml2argvtest and qemuxml2xmltest.
