Ingo Molnar <mingo@xxxxxxx> writes: > * Suresh Siddha <suresh.b.siddha@xxxxxxxxx> wrote: > >> On Wed, 2009-07-01 at 06:30 -0700, Gleb Natapov wrote: >> > KVM would like to provide x2APIC interface to a guest without emulating >> > interrupt remapping device. The reason KVM prefers guest to use x2APIC >> > is that x2APIC interface is better virtualizable and provides better >> > performance than mmio xAPIC interface: >> > >> > - msr exits are faster than mmio (no page table walk, emulation) >> > - no need to read back ICR to look at the busy bit >> > - one 64 bit ICR write instead of two 32 bit writes >> > - shared code with the Hyper-V paravirt interface >> > >> > Included patch changes x2APIC enabling logic to enable it even if IR >> > initialization failed, but kernel runs under KVM and no apic id is >> > greater than 255 (if there is one spec requires BIOS to move to x2apic >> > mode before starting an OS). >> > >> > Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx> >> >> Acked-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx> > > Now, since this affects core x86 APIC code non-trivially so should > submitted to and go via the x86 tree. (Can prepare a special branch > with just this change if KVM tree wants/needs to pull it before > v2.6.32.) Please don't separate the x2apic code from the dmar code for this reason. Supporting hotplug cpus with ioapics is torture. Eric -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
