On 11/25/2012 03:03 PM, Gleb Natapov wrote: > 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? Yes, you're missing the part where I didn't write that the new path should avoid the IDT and dispatch the interrupt directly, by emulating an interrupt frame directly. Can be as simple as pushf; push cs; call interrupt_table[vector * 8]. Of course we need to verify that no interrupt uses the IST or a task gate. -- error compiling committee.c: too many arguments to function -- 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
