From ae7a2a3fb6f8b784c2752863f4f1f20c656f76fb Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Sun, 24 Jun 2012 19:25:07 +0300 Subject: KVM: host side for eoi optimization Implementation of PV EOI using shared memory. This reduces the number of exits an interrupt causes as much as by half. The idea is simple: there's a bit, per APIC, in guest memory, that tells the guest that it does not need EOI. We set it before injecting an interrupt and clear before injecting a nested one. Guest tests it using a test and clear operation - this is necessary so that host can detect interrupt nesting - and if set, it can skip the EOI MSR. There's a new MSR to set the address of said register in guest memory. Otherwise not much changed: - Guest EOI is not required - Register is tested & ISR is automatically cleared on exit For testing results see description of previous patch 'kvm_para: guest side for eoi avoidance'. Signed-off-by: Michael S. Tsirkin Signed-off-by: Avi Kivity --- arch/x86/kvm/cpuid.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/kvm/cpuid.c') diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 7df1c6d839fb..61ccbdf3d0ac 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -409,6 +409,7 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, (1 << KVM_FEATURE_NOP_IO_DELAY) | (1 << KVM_FEATURE_CLOCKSOURCE2) | (1 << KVM_FEATURE_ASYNC_PF) | + (1 << KVM_FEATURE_PV_EOI) | (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT); if (sched_info_on()) -- cgit v1.2.3