It seems that we don't need to take the lock before evaluating irq's
resend flag. What needed is to make sure when we clear the ics's bit
in the icp's resend_map, we don't miss the resend flag of the irqs
that set the bit.
And seems this could be ordered through the barrier in test_and_clear_bit(),
and an newly added wmb when setting irq's resend flag, and icp's resend_map.
Signed-off-by: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kvm/book3s_hv_rm_xics.c | 14 +++++++-------
arch/powerpc/kvm/book3s_xics.c | 22 +++++++---------------
2 files changed, 14 insertions(+), 22 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c b/arch/powerpc/kvm/book3s_hv_rm_xics.c
index c3f604e..c3fa386 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_xics.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -39,14 +39,9 @@ static void ics_rm_check_resend(struct kvmppc_xics *xics,
for (i = 0; i < KVMPPC_XICS_IRQ_PER_ICS; i++) {
struct ics_irq_state *state = &ics->irq_state[i];
- arch_spin_lock(&state->lock);
-
- if (!state->resend) {
- arch_spin_unlock(&state->lock);
+ if (!state->resend)
continue;
- }
- arch_spin_unlock(&state->lock);
icp_rm_deliver_irq(xics, icp, state->number);
}
}
@@ -374,8 +369,13 @@ static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
* We failed to deliver the interrupt we need to set the
* resend map bit and mark the ICS state as needing a resend
*/
- set_bit(ics->icsid, icp->resend_map);
state->resend = 1;
+ /*
+ * Make sure when checking resend, we don't miss the resend if
+ * resend_map bit is seen and cleared.
+ */
+ smp_wmb();
+ set_bit(ics->icsid, icp->resend_map);
/*
* If the need_resend flag got cleared in the ICP some time
diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
index b9dbf75..420c4fc 100644
--- a/arch/powerpc/kvm/book3s_xics.c
+++ b/arch/powerpc/kvm/book3s_xics.c
@@ -110,30 +110,17 @@ static void ics_check_resend(struct kvmppc_xics *xics, struct kvmppc_ics *ics,
{
int i;
- unsigned long flags;
-
- local_irq_save(flags);
-
for (i = 0; i < KVMPPC_XICS_IRQ_PER_ICS; i++) {
struct ics_irq_state *state = &ics->irq_state[i];
- arch_spin_lock(&state->lock);
-
- if (!state->resend) {
- arch_spin_unlock(&state->lock);
+ if (!state->resend)
continue;
- }
XICS_DBG("resend %#x prio %#x\n", state->number,
state->priority);
- arch_spin_unlock(&state->lock);
- local_irq_restore(flags);
icp_deliver_irq(xics, icp, state->number);
- local_irq_save(flags);
}
-
- local_irq_restore(flags);
}
static bool write_xive(struct kvmppc_xics *xics, struct kvmppc_ics *ics,
@@ -474,8 +461,13 @@ static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
* We failed to deliver the interrupt we need to set the
* resend map bit and mark the ICS state as needing a resend
*/
- set_bit(ics->icsid, icp->resend_map);
state->resend = 1;
+ /*
+ * Make sure when checking resend, we don't miss the resend if
+ * resend_map bit is seen and cleared.
+ */
+ smp_wmb();
+ set_bit(ics->icsid, icp->resend_map);
/*
* If the need_resend flag got cleared in the ICP some time
--
1.8.3.1
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