From f85f6e7bc9682a6d8b342c010cd6aa58521fdeec Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Tue, 11 Jun 2019 20:23:48 +0800 Subject: KVM: X86: Yield to IPI target if necessary MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When sending a call-function IPI-many to vCPUs, yield if any of the IPI target vCPUs was preempted, we just select the first preempted target vCPU which we found since the state of target vCPUs can change underneath and to avoid race conditions. Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Liran Alon Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kernel/kvm.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 5169b8cc35bb..82caf01b63dd 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -527,6 +527,21 @@ static void kvm_setup_pv_ipi(void) pr_info("KVM setup pv IPIs\n"); } +static void kvm_smp_send_call_func_ipi(const struct cpumask *mask) +{ + int cpu; + + native_send_call_func_ipi(mask); + + /* Make sure other vCPUs get a chance to run if they need to. */ + for_each_cpu(cpu, mask) { + if (vcpu_is_preempted(cpu)) { + kvm_hypercall1(KVM_HC_SCHED_YIELD, per_cpu(x86_cpu_to_apicid, cpu)); + break; + } + } +} + static void __init kvm_smp_prepare_cpus(unsigned int max_cpus) { native_smp_prepare_cpus(max_cpus); @@ -638,6 +653,12 @@ static void __init kvm_guest_init(void) #ifdef CONFIG_SMP smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus; smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; + if (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) && + !kvm_para_has_hint(KVM_HINTS_REALTIME) && + kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { + smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi; + pr_info("KVM setup pv sched yield\n"); + } if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online", kvm_cpu_online, kvm_cpu_down_prepare) < 0) pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n"); -- cgit v1.2.3