Commit 1da4e2f4 authored by Paul Mackerras's avatar Paul Mackerras
Browse files

KVM: PPC: Book3S HV: Don't let VCPU sleep if it has a doorbell pending 



It is possible, through a narrow race condition, for a VCPU to exit
the guest with a H_CEDE hypercall while it has a doorbell interrupt
pending.  In this case, the H_CEDE should return immediately, but in
fact it puts the VCPU to sleep until some other interrupt becomes
pending or a prod is received (via another VCPU doing H_PROD).

This fixes it by checking the DPDES (Directed Privileged Doorbell
Exception Status) bit for the thread along with the other interrupt
pending bits.

Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent 1bc3fe81

arch/powerpc/kvm/book3s_hv.c

+22 −3
Original line number Diff line number Diff line
@@ -675,6 +675,17 @@ static void kvmppc_create_dtl_entry(struct kvm_vcpu *vcpu, 
	vcpu->arch.dtl.dirty = true;

}



/* See if there is a doorbell interrupt pending for a vcpu */

static bool kvmppc_doorbell_pending(struct kvm_vcpu *vcpu)

{

	int thr;

	struct kvmppc_vcore *vc;



	vc = vcpu->arch.vcore;

	thr = vcpu->vcpu_id - vc->first_vcpuid;

	return !!(vc->dpdes & (1 << thr));

}



static bool kvmppc_power8_compatible(struct kvm_vcpu *vcpu)

{

	if (vcpu->arch.vcore->arch_compat >= PVR_ARCH_207)
@@ -2672,6 +2683,15 @@ static void shrink_halt_poll_ns(struct kvmppc_vcore *vc) 
		vc->halt_poll_ns /= halt_poll_ns_shrink;

}



static bool kvmppc_vcpu_woken(struct kvm_vcpu *vcpu)

{

	if (vcpu->arch.pending_exceptions || vcpu->arch.prodded ||

	    kvmppc_doorbell_pending(vcpu))

		return true;



	return false;

}



/*

 * Check to see if any of the runnable vcpus on the vcore have pending

 * exceptions or are no longer ceded
@@ -2682,8 +2702,7 @@ static int kvmppc_vcore_check_block(struct kvmppc_vcore *vc) 
	int i;



	for_each_runnable_thread(i, vcpu, vc) {

		if (vcpu->arch.pending_exceptions || !vcpu->arch.ceded ||

		    vcpu->arch.prodded)

		if (!vcpu->arch.ceded || kvmppc_vcpu_woken(vcpu))

			return 1;

	}
@@ -2869,7 +2888,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) 
			break;

		n_ceded = 0;

		for_each_runnable_thread(i, v, vc) {

			if (!v->arch.pending_exceptions && !v->arch.prodded)

			if (!kvmppc_vcpu_woken(v))

				n_ceded += v->arch.ceded;

			else

				v->arch.ceded = 0;

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