From 53258205854e649bc82310542373df004a4734ab Mon Sep 17 00:00:00 2001 From: Michal Privoznik Date: Thu, 4 Jan 2024 10:03:36 +0100 Subject: [PATCH] conf: Introduce dynamicMemslots attribute for virtio-mem Introduced in v8.2.0-rc0~74^2~2, QEMU now allows setting .dynamic-memslots attribute for virtio-mem-pci devices. When turned on, it allows memory exposed to guest to be split into multiple memslots and thus smaller memory footprint (see the original commit for detailed explanation). Therefore, introduce new attribute which will control that QEMU knob. Signed-off-by: Michal Privoznik Reviewed-by: Peter Krempa --- docs/formatdomain.rst | 13 +++++++++++++ src/conf/domain_conf.c | 18 +++++++++++++++++- src/conf/domain_conf.h | 1 + src/conf/schemas/domaincommon.rng | 5 +++++ .../memory-hotplug-virtio-mem.xml | 2 +- 5 files changed, 37 insertions(+), 2 deletions(-) diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst index 67d5f958d5..0a4f9d9000 100644 --- a/docs/formatdomain.rst +++ b/docs/formatdomain.rst @@ -8443,6 +8443,19 @@ Example: usage of the memory devices The ``node`` subelement configures the guest NUMA node to attach the memory to. The element shall be used only if the guest has NUMA nodes configured. + For ``virtio-mem`` optional attribute ``dynamicMemslots`` can be specified + (accepted values "yes"/"no") which allows hypervisor to spread memory into + multiple memory slots (allocate them dynamically based on the amount of + memory exposed to the guest), resulting in smaller memory footprint. But be + aware this may affect vhost-user devices. When enabled, older vhost-user + device implementations (such as virtiofs) may refuse to initialize resulting + in failed domain startup or device hotplug. When only modern vhost-user + based devices will be used or when no vhost-user devices are expected to be + used it's beneficial to enable this feature. The current default is + hypervisor dependant (for QEMU is "no"). If the default changes and you are + having difficulties with vhost-user devices, try toggling this to "no". + :since:`Since 10.1.0 and QEMU 8.2.0` + The following optional elements may be used: ``label`` diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 59d51c4c52..fb5a5cc351 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -13558,6 +13558,10 @@ virDomainMemoryTargetDefParseXML(xmlNodePtr node, &def->target.virtio_mem.requestedsize, false, false) < 0) return -1; + if (virXMLPropTristateBool(node, "dynamicMemslots", VIR_XML_PROP_NONE, + &def->target.virtio_mem.dynamicMemslots) < 0) + return -1; + addrNode = virXPathNode("./address", ctxt); addr = &def->target.virtio_mem.address; break; @@ -21232,6 +21236,12 @@ virDomainMemoryDefCheckABIStability(virDomainMemoryDef *src, src->target.virtio_mem.address); return false; } + + if (src->target.virtio_mem.dynamicMemslots != dst->target.virtio_mem.dynamicMemslots) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("Target memory device 'dynamicMemslots' property doesn't match source memory device")); + return false; + } break; case VIR_DOMAIN_MEMORY_MODEL_DIMM: @@ -25448,6 +25458,7 @@ virDomainMemoryTargetDefFormat(virBuffer *buf, unsigned int flags) { g_auto(virBuffer) childBuf = VIR_BUFFER_INIT_CHILD(buf); + g_auto(virBuffer) attrBuf = VIR_BUFFER_INITIALIZER; virBufferAsprintf(&childBuf, "%llu\n", def->size); if (def->targetNode >= 0) @@ -25487,6 +25498,11 @@ virDomainMemoryTargetDefFormat(virBuffer *buf, if (def->target.virtio_mem.address) virBufferAsprintf(&childBuf, "
\n", def->target.virtio_mem.address); + + if (def->target.virtio_mem.dynamicMemslots) { + virBufferAsprintf(&attrBuf, " dynamicMemslots='%s'", + virTristateBoolTypeToString(def->target.virtio_mem.dynamicMemslots)); + } break; case VIR_DOMAIN_MEMORY_MODEL_SGX_EPC: @@ -25496,7 +25512,7 @@ virDomainMemoryTargetDefFormat(virBuffer *buf, break; } - virXMLFormatElement(buf, "target", NULL, &childBuf); + virXMLFormatElement(buf, "target", &attrBuf, &childBuf); } static int diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index d176bda5f8..bd283d42df 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -2676,6 +2676,7 @@ struct _virDomainMemoryDef { unsigned long long currentsize; /* kibibytes, valid for an active domain only and parsed */ unsigned long long address; /* address where memory is mapped */ + virTristateBool dynamicMemslots; } virtio_mem; struct { } sgx_epc; diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng index a34427c330..df44cd9857 100644 --- a/src/conf/schemas/domaincommon.rng +++ b/src/conf/schemas/domaincommon.rng @@ -7268,6 +7268,11 @@ + + + + + diff --git a/tests/qemuxmlconfdata/memory-hotplug-virtio-mem.xml b/tests/qemuxmlconfdata/memory-hotplug-virtio-mem.xml index 52fa6b14e9..20282a131b 100644 --- a/tests/qemuxmlconfdata/memory-hotplug-virtio-mem.xml +++ b/tests/qemuxmlconfdata/memory-hotplug-virtio-mem.xml @@ -60,7 +60,7 @@ 1-3 2048 - + 2097152 0 2048