KVM: x86: fix deadlock in clock-in-progress request handling (c09664bb) · Commits · 戴 / test

There is a deadlock in pvclock handling: cpu0: cpu1: kvm_gen_update_masterclock() kvm_guest_time_update() spin_lock(pvclock_gtod_sync_lock) local_irq_save(flags) spin_lock(pvclock_gtod_sync_lock) kvm_make_mclock_inprogress_request(kvm) make_all_cpus_request() smp_call_function_many() Now if smp_call_function_many() called by cpu0 tries to call function on cpu1 there will be a deadlock. Fix by moving pvclock_gtod_sync_lock protected section outside irq disabled section. Analyzed by Gleb Natapov <gleb@redhat.com> Acked-by:

Gleb Natapov <gleb@redhat.com> Reported-and-Tested-by:

Yongjie Ren <yongjie.ren@intel.com> Signed-off-by:

Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

+9 −9

Original line number	Diff line number	Diff line
		@@ -1416,15 +1416,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
		kernel_ns = 0;
		host_tsc = 0;

		/* Keep irq disabled to prevent changes to the clock */
		local_irq_save(flags);
		this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
		if (unlikely(this_tsc_khz == 0)) {
		local_irq_restore(flags);
		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
		return 1;
		}

		/*
		* If the host uses TSC clock, then passthrough TSC as stable
		* to the guest.
		@@ -1436,6 +1427,15 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
		kernel_ns = ka->master_kernel_ns;
		}
		spin_unlock(&ka->pvclock_gtod_sync_lock);

		/* Keep irq disabled to prevent changes to the clock */
		local_irq_save(flags);
		this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
		if (unlikely(this_tsc_khz == 0)) {
		local_irq_restore(flags);
		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
		return 1;
		}
		if (!use_master_clock) {
		host_tsc = native_read_tsc();
		kernel_ns = get_kernel_ns();

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