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Commit 53655ddd authored by Paul Mackerras's avatar Paul Mackerras Committed by Michael Ellerman
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KVM: PPC: Book3S HV: Call kvmppc_handle_exit_hv() with vcore unlocked 



Currently kvmppc_handle_exit_hv() is called with the vcore lock held
because it is called within a for_each_runnable_thread loop.
However, we already unlock the vcore within kvmppc_handle_exit_hv()
under certain circumstances, and this is safe because (a) any vcpus
that become runnable and are added to the runnable set by
kvmppc_run_vcpu() have their vcpu->arch.trap == 0 and can't actually
run in the guest (because the vcore state is VCORE_EXITING), and
(b) for_each_runnable_thread is safe against addition or removal
of vcpus from the runnable set.

Therefore, in order to simplify things for following patches, let's
drop the vcore lock in the for_each_runnable_thread loop, so
kvmppc_handle_exit_hv() gets called without the vcore lock held.

Reviewed-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 7854f754

arch/powerpc/kvm/book3s_hv.c

+10 −9
Original line number Diff line number Diff line
@@ -1084,7 +1084,6 @@ static int kvmppc_emulate_doorbell_instr(struct kvm_vcpu *vcpu) 
	return RESUME_GUEST;

}



/* Called with vcpu->arch.vcore->lock held */

static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,

				 struct task_struct *tsk)

{
@@ -1205,10 +1204,7 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu, 
				swab32(vcpu->arch.emul_inst) :

				vcpu->arch.emul_inst;

		if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {

			/* Need vcore unlocked to call kvmppc_get_last_inst */

			spin_unlock(&vcpu->arch.vcore->lock);

			r = kvmppc_emulate_debug_inst(run, vcpu);

			spin_lock(&vcpu->arch.vcore->lock);

		} else {

			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);

			r = RESUME_GUEST;
@@ -1224,12 +1220,8 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu, 
	case BOOK3S_INTERRUPT_H_FAC_UNAVAIL:

		r = EMULATE_FAIL;

		if (((vcpu->arch.hfscr >> 56) == FSCR_MSGP_LG) &&

		    cpu_has_feature(CPU_FTR_ARCH_300)) {

			/* Need vcore unlocked to call kvmppc_get_last_inst */

			spin_unlock(&vcpu->arch.vcore->lock);

		    cpu_has_feature(CPU_FTR_ARCH_300))

			r = kvmppc_emulate_doorbell_instr(vcpu);

			spin_lock(&vcpu->arch.vcore->lock);

		}

		if (r == EMULATE_FAIL) {

			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);

			r = RESUME_GUEST;
@@ -2599,6 +2591,14 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master) 
	spin_lock(&vc->lock);

	now = get_tb();

	for_each_runnable_thread(i, vcpu, vc) {

		/*

		 * It's safe to unlock the vcore in the loop here, because

		 * for_each_runnable_thread() is safe against removal of

		 * the vcpu, and the vcore state is VCORE_EXITING here,

		 * so any vcpus becoming runnable will have their arch.trap

		 * set to zero and can't actually run in the guest.

		 */

		spin_unlock(&vc->lock);

		/* cancel pending dec exception if dec is positive */

		if (now < vcpu->arch.dec_expires &&

		    kvmppc_core_pending_dec(vcpu))
@@ -2614,6 +2614,7 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master) 
		vcpu->arch.ret = ret;

		vcpu->arch.trap = 0;



		spin_lock(&vc->lock);

		if (is_kvmppc_resume_guest(vcpu->arch.ret)) {

			if (vcpu->arch.pending_exceptions)

				kvmppc_core_prepare_to_enter(vcpu);