This patch improves the code that takes lock twice to check the resend flag
and do the actual resending, by checking the resend flag locklessly, and
add a boolean parameter check_resend to icp_[rm_]deliver_irq(), so the
resend flag can be checked in the lock when doing the delivery.
We need 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. It could be
ordered through the barrier in test_and_clear_bit(), and a newly added
wmb between setting irq's resend flag, and icp's resend_map.
Signed-off-by: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Paul Mackerras <paulus@xxxxxxxxxx>
---
arch/powerpc/kvm/book3s_hv_rm_xics.c | 40 ++++++++++++------------
arch/powerpc/kvm/book3s_xics.c | 59 +++++++++++++++++-------------------
2 files changed, 48 insertions(+), 51 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c b/arch/powerpc/kvm/book3s_hv_rm_xics.c
index f1f579f..24575de 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_xics.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -35,7 +35,7 @@
EXPORT_SYMBOL(kvm_irq_bypass);
static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
- u32 new_irq);
+ u32 new_irq, bool check_resend);
static int xics_opal_rm_set_server(unsigned int hw_irq, int server_cpu);
/* -- ICS routines -- */
@@ -44,22 +44,12 @@ static void ics_rm_check_resend(struct kvmppc_xics *xics,
{
int i;
- arch_spin_lock(&ics->lock);
-
for (i = 0; i < KVMPPC_XICS_IRQ_PER_ICS; i++) {
struct ics_irq_state *state = &ics->irq_state[i];
-
- if (!state->resend)
- continue;
-
- state->resend = 0;
-
- arch_spin_unlock(&ics->lock);
- icp_rm_deliver_irq(xics, icp, state->number);
- arch_spin_lock(&ics->lock);
+ if (state->resend)
+ icp_rm_deliver_irq(xics, icp, state->number, true);
}
- arch_spin_unlock(&ics->lock);
}
/* -- ICP routines -- */
@@ -288,7 +278,7 @@ static bool icp_rm_try_to_deliver(struct kvmppc_icp *icp, u32 irq, u8 priority,
}
static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
- u32 new_irq)
+ u32 new_irq, bool check_resend)
{
struct ics_irq_state *state;
struct kvmppc_ics *ics;
@@ -333,6 +323,10 @@ static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
}
}
+ if (check_resend)
+ if (!state->resend)
+ goto out;
+
/* Clear the resend bit of that interrupt */
state->resend = 0;
@@ -380,6 +374,7 @@ static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
arch_spin_unlock(&ics->lock);
icp->n_reject++;
new_irq = reject;
+ check_resend = 0;
goto again;
}
} else {
@@ -387,10 +382,16 @@ 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
* between icp_rm_try_to_deliver() atomic update and now, then
* we know it might have missed the resend_map bit. So we
@@ -400,6 +401,7 @@ static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
if (!icp->state.need_resend) {
state->resend = 0;
arch_spin_unlock(&ics->lock);
+ check_resend = 0;
goto again;
}
}
@@ -594,7 +596,7 @@ int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
/* Handle reject in real mode */
if (reject && reject != XICS_IPI) {
this_icp->n_reject++;
- icp_rm_deliver_irq(xics, icp, reject);
+ icp_rm_deliver_irq(xics, icp, reject, false);
}
/* Handle resends in real mode */
@@ -662,7 +664,7 @@ int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
*/
if (reject && reject != XICS_IPI) {
icp->n_reject++;
- icp_rm_deliver_irq(xics, icp, reject);
+ icp_rm_deliver_irq(xics, icp, reject, false);
}
bail:
return check_too_hard(xics, icp);
@@ -700,7 +702,7 @@ static int ics_rm_eoi(struct kvm_vcpu *vcpu, u32 irq)
} while (cmpxchg(&state->pq_state, pq_old, pq_new) != pq_old);
if (pq_new & PQ_PRESENTED)
- icp_rm_deliver_irq(xics, NULL, irq);
+ icp_rm_deliver_irq(xics, NULL, irq, false);
if (!hlist_empty(&vcpu->kvm->irq_ack_notifier_list)) {
icp->rm_action |= XICS_RM_NOTIFY_EOI;
@@ -864,7 +866,7 @@ long kvmppc_deliver_irq_passthru(struct kvm_vcpu *vcpu,
/* Test P=1, Q=0, this is the only case where we present */
if (pq_new == PQ_PRESENTED)
- icp_rm_deliver_irq(xics, icp, irq);
+ icp_rm_deliver_irq(xics, icp, irq, false);
/* EOI the interrupt */
icp_eoi(irq_desc_get_chip(irq_map->desc), irq_map->r_hwirq, xirr);
diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
index e9ba11e..c931fdc 100644
--- a/arch/powerpc/kvm/book3s_xics.c
+++ b/arch/powerpc/kvm/book3s_xics.c
@@ -63,7 +63,7 @@
/* -- ICS routines -- */
static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
- u32 new_irq);
+ u32 new_irq, bool check_resend);
/*
* Return value ideally indicates how the interrupt was handled, but no
@@ -117,7 +117,7 @@ static int ics_deliver_irq(struct kvmppc_xics *xics, u32 irq, u32 level)
/* Test P=1, Q=0, this is the only case where we present */
if (pq_new == PQ_PRESENTED)
- icp_deliver_irq(xics, NULL, irq);
+ icp_deliver_irq(xics, NULL, irq, false);
/* Record which CPU this arrived on for passed-through interrupts */
if (state->host_irq)
@@ -131,31 +131,14 @@ static void ics_check_resend(struct kvmppc_xics *xics, struct kvmppc_ics *ics,
{
int i;
- unsigned long flags;
-
- local_irq_save(flags);
- arch_spin_lock(&ics->lock);
-
for (i = 0; i < KVMPPC_XICS_IRQ_PER_ICS; i++) {
struct ics_irq_state *state = &ics->irq_state[i];
-
- if (!state->resend)
- continue;
-
- state->resend = 0;
-
- XICS_DBG("resend %#x prio %#x\n", state->number,
- state->priority);
-
- arch_spin_unlock(&ics->lock);
- local_irq_restore(flags);
- icp_deliver_irq(xics, icp, state->number);
- local_irq_save(flags);
- arch_spin_lock(&ics->lock);
+ if (state->resend) {
+ XICS_DBG("resend %#x prio %#x\n", state->number,
+ state->priority);
+ icp_deliver_irq(xics, icp, state->number, true);
+ }
}
-
- arch_spin_unlock(&ics->lock);
- local_irq_restore(flags);
}
static bool write_xive(struct kvmppc_xics *xics, struct kvmppc_ics *ics,
@@ -209,7 +192,7 @@ int kvmppc_xics_set_xive(struct kvm *kvm, u32 irq, u32 server, u32 priority)
state->masked_pending, state->resend);
if (write_xive(xics, ics, state, server, priority, priority))
- icp_deliver_irq(xics, icp, irq);
+ icp_deliver_irq(xics, icp, irq, false);
return 0;
}
@@ -262,7 +245,7 @@ int kvmppc_xics_int_on(struct kvm *kvm, u32 irq)
if (write_xive(xics, ics, state, state->server, state->saved_priority,
state->saved_priority))
- icp_deliver_irq(xics, icp, irq);
+ icp_deliver_irq(xics, icp, irq, false);
return 0;
}
@@ -396,7 +379,7 @@ static bool icp_try_to_deliver(struct kvmppc_icp *icp, u32 irq, u8 priority,
}
static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
- u32 new_irq)
+ u32 new_irq, bool check_resend)
{
struct ics_irq_state *state;
struct kvmppc_ics *ics;
@@ -442,6 +425,10 @@ static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
}
}
+ if (check_resend)
+ if (!state->resend)
+ goto out;
+
/* Clear the resend bit of that interrupt */
state->resend = 0;
@@ -490,6 +477,7 @@ static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
arch_spin_unlock(&ics->lock);
local_irq_restore(flags);
new_irq = reject;
+ check_resend = 0;
goto again;
}
} else {
@@ -497,10 +485,16 @@ 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
* between icp_try_to_deliver() atomic update and now, then
* we know it might have missed the resend_map bit. So we
@@ -511,6 +505,7 @@ static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
state->resend = 0;
arch_spin_unlock(&ics->lock);
local_irq_restore(flags);
+ check_resend = 0;
goto again;
}
}
@@ -702,7 +697,7 @@ static noinline int kvmppc_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
/* Handle reject */
if (reject && reject != XICS_IPI)
- icp_deliver_irq(xics, icp, reject);
+ icp_deliver_irq(xics, icp, reject, false);
/* Handle resend */
if (resend)
@@ -782,7 +777,7 @@ static noinline void kvmppc_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
* attempt (see comments in icp_deliver_irq).
*/
if (reject && reject != XICS_IPI)
- icp_deliver_irq(xics, icp, reject);
+ icp_deliver_irq(xics, icp, reject, false);
}
static int ics_eoi(struct kvm_vcpu *vcpu, u32 irq)
@@ -818,7 +813,7 @@ static int ics_eoi(struct kvm_vcpu *vcpu, u32 irq)
} while (cmpxchg(&state->pq_state, pq_old, pq_new) != pq_old);
if (pq_new & PQ_PRESENTED)
- icp_deliver_irq(xics, icp, irq);
+ icp_deliver_irq(xics, icp, irq, false);
kvm_notify_acked_irq(vcpu->kvm, 0, irq);
@@ -1307,7 +1302,7 @@ static int xics_set_source(struct kvmppc_xics *xics, long irq, u64 addr)
local_irq_restore(flags);
if (val & KVM_XICS_PENDING)
- icp_deliver_irq(xics, NULL, irqp->number);
+ icp_deliver_irq(xics, NULL, irqp->number, false);
return 0;
}
--
1.9.1
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