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Commit bf5a71d5 authored by Li Zhong's avatar Li Zhong Committed by Paul Mackerras
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KVM: PPC: Book 3S: XICS: Fix potential issue with duplicate IRQ resends 



It is possible that in the following order, one irq is resent twice:

        CPU 1                                   CPU 2

ics_check_resend()
  lock ics_lock
    see resend set
  unlock ics_lock
                                       /* change affinity of the irq */
                                       kvmppc_xics_set_xive()
                                         write_xive()
                                           lock ics_lock
                                             see resend set
                                           unlock ics_lock

                                         icp_deliver_irq() /* resend */

  icp_deliver_irq() /* resend again */

It doesn't have any user-visible effect at present, but needs to be avoided
when the following patch implementing the P/Q stuff is applied.

This patch clears the resend flag before releasing the ics lock, when we
know we will do a re-delivery after checking the flag, or setting the flag.

Signed-off-by: default avatarLi Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent 37451bc9

arch/powerpc/kvm/book3s_hv_rm_xics.c

+3 −0
Original line number Original line Diff line number Diff line
@@ -52,6 +52,8 @@ static void ics_rm_check_resend(struct kvmppc_xics *xics, 
		if (!state->resend)

		if (!state->resend)

			continue;

			continue;





		state->resend = 0;



		arch_spin_unlock(&ics->lock);

		arch_spin_unlock(&ics->lock);

		icp_rm_deliver_irq(xics, icp, state->number);

		icp_rm_deliver_irq(xics, icp, state->number);

		arch_spin_lock(&ics->lock);

		arch_spin_lock(&ics->lock);
@@ -400,6 +402,7 @@ static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp, 
		 */

		 */

		smp_mb();

		smp_mb();

		if (!icp->state.need_resend) {

		if (!icp->state.need_resend) {

			state->resend = 0;

			arch_spin_unlock(&ics->lock);

			arch_spin_unlock(&ics->lock);

			goto again;

			goto again;

		}

		}

arch/powerpc/kvm/book3s_xics.c

+4 −0
Original line number Original line Diff line number Diff line
@@ -125,6 +125,8 @@ static void ics_check_resend(struct kvmppc_xics *xics, struct kvmppc_ics *ics, 
		if (!state->resend)

		if (!state->resend)

			continue;

			continue;





		state->resend = 0;



		XICS_DBG("resend %#x prio %#x\n", state->number,

		XICS_DBG("resend %#x prio %#x\n", state->number,

			      state->priority);

			      state->priority);
@@ -155,6 +157,7 @@ static bool write_xive(struct kvmppc_xics *xics, struct kvmppc_ics *ics, 
	deliver = false;

	deliver = false;

	if ((state->masked_pending || state->resend) && priority != MASKED) {

	if ((state->masked_pending || state->resend) && priority != MASKED) {

		state->masked_pending = 0;

		state->masked_pending = 0;

		state->resend = 0;

		deliver = true;

		deliver = true;

	}

	}
@@ -488,6 +491,7 @@ static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp, 
		 */

		 */

		smp_mb();

		smp_mb();

		if (!icp->state.need_resend) {

		if (!icp->state.need_resend) {

			state->resend = 0;

			arch_spin_unlock(&ics->lock);

			arch_spin_unlock(&ics->lock);

			local_irq_restore(flags);

			local_irq_restore(flags);

			goto again;

			goto again;