KVM: grow_halt_poll_ns() should never shrink vCPU halt_poll_ns (7fa08e71) · Commits · 戴 / test

grow_halt_poll_ns() have a strange behavior in case (halt_poll_ns_grow == 0) && (vcpu->halt_poll_ns != 0). In this case, vcpu->halt_pol_ns will be set to zero. That results in shrinking instead of growing. Fix issue by changing grow_halt_poll_ns() to not modify vcpu->halt_poll_ns in case halt_poll_ns_grow is zero Reviewed-by:

Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by:

Liran Alon <liran.alon@oracle.com> Signed-off-by:

Nir Weiner <nir.weiner@oracle.com> Suggested-by:

Liran Alon <liran.alon@oracle.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/powerpc/kvm/book3s_hv.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -3631,8 +3631,11 @@ static void kvmppc_wait_for_exec(struct kvmppc_vcore *vc,

		static void grow_halt_poll_ns(struct kvmppc_vcore *vc)
		{
		if (!halt_poll_ns_grow)
		return;

		/* 10us base */
		if (vc->halt_poll_ns == 0 && halt_poll_ns_grow)
		if (vc->halt_poll_ns == 0)
		vc->halt_poll_ns = 10000;
		else
		vc->halt_poll_ns *= halt_poll_ns_grow;

virt/kvm/kvm_main.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -2188,8 +2188,11 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)

		old = val = vcpu->halt_poll_ns;
		grow = READ_ONCE(halt_poll_ns_grow);
		if (!grow)
		goto out;

		/* 10us base */
		if (val == 0 && grow)
		if (val == 0)
		val = 10000;
		else
		val *= grow;
		@@ -2198,6 +2201,7 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
		val = halt_poll_ns;

		vcpu->halt_poll_ns = val;
		out:
		trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
		}

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