On Sat, Jul 04, 2009 at 02:35:30AM -0700, Eric W. Biederman wrote: > 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. > What is the connection between this patch and cpu hotplug? -- Gleb. -- 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
