ce69a78450
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). -v2: fix build -v3: fix bug causing compiler warning Signed-off-by: Gleb Natapov <gleb@redhat.com> Acked-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Sheng Yang <sheng@linux.intel.com> Cc: "avi@redhat.com" <avi@redhat.com> LKML-Reference: <20090720122417.GR5638@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
||
|---|---|---|
| .. | ||
| asm | ||