On Sun, Nov 25, 2012 at 02:55:26PM +0200, Avi Kivity wrote: > On 11/22/2012 05:22 PM, Gleb Natapov wrote: > > On Wed, Nov 21, 2012 at 04:09:38PM +0800, Yang Zhang wrote: > >> Ack interrupt on vmexit is required by Posted Interrupt. With it, > >> when external interrupt caused vmexit, the cpu will acknowledge the > >> interrupt controller and save the interrupt's vector in vmcs. > >> > >> There are several approaches to enable it. This patch uses a simply > >> way: re-generate an interrupt via self ipi. > >> > >> > >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > >> index 7949d21..f6ef090 100644 > >> --- a/arch/x86/kvm/vmx.c > >> +++ b/arch/x86/kvm/vmx.c > >> @@ -2525,7 +2525,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf) > >> #ifdef CONFIG_X86_64 > >> min |= VM_EXIT_HOST_ADDR_SPACE_SIZE; > >> #endif > >> - opt = VM_EXIT_SAVE_IA32_PAT | VM_EXIT_LOAD_IA32_PAT; > >> + opt = VM_EXIT_SAVE_IA32_PAT | VM_EXIT_LOAD_IA32_PAT | > >> + VM_EXIT_ACK_INTR_ON_EXIT; > > Always? Do it only if posted interrupts are actually available > > and going to be used. > > Why not always? Better to have a single code path for host interrupts > (and as Yang notes, the new path is faster as well). > Is it? The current path is: vm exit -> KVM vmexit handler(interrupt disabled) -> KVM re-enable interrupt -> cpu ack the interrupt and interrupt deliver through the host IDT. The proposed path is: CPU acks interrupt -> vm exit -> KVM vmexit handler(interrupt disabled) -> eoi -> self IPI -> KVM re-enable interrupt -> cpu ack the interrupt and interrupt deliver through the host IDT. Am I missing something? -- 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
