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KVM: PPC: Book 3S: XICS: Don't lock twice when checking for resend

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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@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Li Zhong 2016-11-11 12:57:36 +08:00 committed by Paul Mackerras
parent 17d48610ae
commit 21acd0e4df
2 changed files with 48 additions and 51 deletions
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40
arch/powerpc/kvm/book3s_hv_rm_xics.c
View File

@ -35,7 +35,7 @@ int kvm_irq_bypass = 1;
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 -- */
@ -292,7 +282,7 @@ 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;
@ -337,6 +327,10 @@ 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;
@ -384,6 +378,7 @@ 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 {
@ -391,9 +386,15 @@ 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
@ -404,6 +405,7 @@ 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;
}
}
@ -598,7 +600,7 @@ 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 */
@ -666,7 +668,7 @@ 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);
@ -704,7 +706,7 @@ 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;
@ -874,7 +876,7 @@ 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,

59
arch/powerpc/kvm/book3s_xics.c
View File

@ -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 {
@ -497,9 +485,15 @@ 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
@ -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;
}