The improved interface reduces the number of needed APIC register accesses for sending [[inter-processor interrupt]]s (IPIs). Because of this advantage, [[Kernel-based Virtual Machine|KVM]] can and does emulate the x2APIC for older processors that do not physically support it, and this support is exposed from [[QEMU]] going back to [[Conroe (microprocessor)|Conroe]] and even for AMD [[Opteron]] G-series processors (neither of which natively support x2APIC).<ref>{{cite web|url=https://lists.gnu.org/archive/html/qemu-devel/2013-07/msg03756.html|title=Re: [Qemu-devel] [Question] why x2apic's set by default without host sup|website=lists.gnu.org}}</ref><ref>{{cite web|url=http://lists.nongnu.org/archive/html/qemu-devel/2014-01/msg02441.html|title=[Qemu-devel] [PATCH] target-i386: enable x2apic by default on more recen|website=lists.nongnu.org}}</ref>
[[APICv]] is the Intel's brand name for [[hardware virtualization]] support aimed at reducing interrupt overhead in guests. APICv was introduced in the [[Ivy Bridge-EP]] processor series, which is sold as Xeon E5-26xx v2 (launched in late 2013) and as Xeon E5-46xx v2 (launched in early 2014).<ref>{{cite web |author=Jun Nakajima |title=Reviewing Unused and New Features for Interrupt/APIC Virtualization |url=http://www.linuxplumbersconf.org/2012/wp-content/uploads/2012/09/2012-lpc-virt-intel-vt-feat-nakajima.pdf |website=Linux |access-date=14 May 2023 |year=2012}}</ref><ref>{{cite web|url=https://software.intel.com/en-us/blogs/2013/12/17/apic-virtualization-performance-testing-and-iozone|title=APIC Virtualization Performance Testing and Iozone* - Intel® Software|website=software.intel.com}}</ref> AMD announced a similar technology called [[Advanced Virtual Interrupt Controller|AVIC]],<ref>Wei Huang, [http://www.slideshare.net/xen_com_mgr/introduction-of-amd-virtual-interrupt-controller Introduction of AMD Advanced Virtual Interrupt Controller], XenSummit 2012</ref><ref>{{cite web |author=Jörg Rödel |title=Next-generation Interrupt Virtualization for KVM |url=http://www.linuxplumbersconf.org/2012/wp-content/uploads/2012/09/2012-lpc-virt-interrupt-virt-kvm-roedel.pdf |website=Linux |access-date=14 May 2023 |date=August 2012}}</ref> it is available family [[Excavator (microarchitecture)|15h models 6Xh (Carrizo) processors]] and newer.<ref>{{cite web|url=https://www.mail-archive.com/xen-devel@lists.xen.org/msg81719.html|title=[Xen-devel] [RFC PATCH 0/9] Introduce AMD SVM AVIC|website=www.mail-archive.com}}</ref>
