KVM: LAPIC: Enable timer posted-interrupt only when mwait/hlt is advertised

stable inclusion
from stable-v5.10.115
commit 43dbc3edada66eaa9d406ea9647359e795288ea0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5IZ9C

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=43dbc3edada66eaa9d406ea9647359e795288ea0

--------------------------------

[ Upstream commit 1714a4eb ]

As commit 0c5f81da ("KVM: LAPIC: Inject timer interrupt via posted
interrupt") mentioned that the host admin should well tune the guest
setup, so that vCPUs are placed on isolated pCPUs, and with several pCPUs
surplus for *busy* housekeeping.  In this setup, it is preferrable to
disable mwait/hlt/pause vmexits to keep the vCPUs in non-root mode.

However, if only some guests isolated and others not, they would not
have any benefit from posted timer interrupts, and at the same time lose
VMX preemption timer fast paths because kvm_can_post_timer_interrupt()
returns true and therefore forces kvm_can_use_hv_timer() to false.

By guaranteeing that posted-interrupt timer is only used if MWAIT or
HLT are done without vmexit, KVM can make a better choice and use the
VMX preemption timer and the corresponding fast paths.
Reported-by: NAili Yao <yaoaili@kingsoft.com>
Reviewed-by: NSean Christopherson <seanjc@google.com>
Cc: Aili Yao <yaoaili@kingsoft.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: NWanpeng Li <wanpengli@tencent.com>
Message-Id: <1643112538-36743-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/x86/kvm/lapic.c

@@ -113,7 +113,8 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
 
 static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu)
 {
-	return pi_inject_timer && kvm_vcpu_apicv_active(vcpu);
+	return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) &&
+		(kvm_mwait_in_guest(vcpu->kvm) || kvm_hlt_in_guest(vcpu->kvm));
 }
 
 bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu)