On 08/23/2011 11:09 AM, Tian, Kevin wrote:
Hi, Avi, Both Eddie and Marcello once suggested vEOI optimization by skipping heavy-weight instruction decode, which reduces vEOI overhead greatly: http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg18619.html http://www.spinics.net/lists/kvm/msg36691.html Though virtual x2apic serves similar purpose, it depends on guest OS to support x2apic. Many Windows versions don't support x2apic though, including Win7, Windows server before 2008 R2, etc. Given that virtualization need support various OS versions, any chance to incorporate above vEOI optimization in KVM as an alternative to boost performance when guest doesn't support x2apic?
Yes. There was a problem with the guest using MOVSD or STOSD to write the EOI; if we don't emulate, then registers don't get updated. I guess we can ignore it since no sane guest will use those instructions for EOI.
Another option is the hyper-V EOI support, which can also eliminate the EOI exit when no additional interrupt is pending. This can improve EOI performance even more.
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