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Subject[PATCH 23/43] KVM: change the way how lowest priority vcpu is calculated
Date
From: Gleb Natapov <gleb@redhat.com>

The new way does not require additional loop over vcpus to calculate
the one with lowest priority as one is chosen during delivery bitmap
construction.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
arch/ia64/kvm/kvm-ia64.c | 15 +-----------
arch/ia64/kvm/lapic.h | 1 +
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/lapic.c | 43 +++++---------------------------------
virt/kvm/ioapic.h | 3 +-
virt/kvm/irq_comm.c | 19 ++++++++++-------
6 files changed, 22 insertions(+), 61 deletions(-)

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 8eea9cb..1887a93 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1836,20 +1836,9 @@ int kvm_apic_match_logical_addr(struct kvm_lapic *apic, u8 mda)
return 0;
}

-struct kvm_vcpu *kvm_get_lowest_prio_vcpu(struct kvm *kvm, u8 vector,
- unsigned long *bitmap)
+int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
{
- struct kvm_vcpu *lvcpu = kvm->vcpus[0];
- int i;
-
- for (i = 1; i < kvm->arch.online_vcpus; i++) {
- if (!kvm->vcpus[i])
- continue;
- if (lvcpu->arch.xtp > kvm->vcpus[i]->arch.xtp)
- lvcpu = kvm->vcpus[i];
- }
-
- return lvcpu;
+ return vcpu1->arch.xtp - vcpu2->arch.xtp;
}

int kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
diff --git a/arch/ia64/kvm/lapic.h b/arch/ia64/kvm/lapic.h
index 31602e7..e42109e 100644
--- a/arch/ia64/kvm/lapic.h
+++ b/arch/ia64/kvm/lapic.h
@@ -22,6 +22,7 @@ int kvm_apic_match_physical_addr(struct kvm_lapic *apic, u16 dest);
int kvm_apic_match_logical_addr(struct kvm_lapic *apic, u8 mda);
int kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
int short_hand, int dest, int dest_mode);
+int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2);
bool kvm_apic_present(struct kvm_vcpu *vcpu);
int kvm_apic_set_irq(struct kvm_vcpu *vcpu, u8 vec, u8 dmode, u8 trig);

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f0faf58..4627627 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -286,6 +286,7 @@ struct kvm_vcpu_arch {
u64 shadow_efer;
u64 apic_base;
struct kvm_lapic *apic; /* kernel irqchip context */
+ int32_t apic_arb_prio;
int mp_state;
int sipi_vector;
u64 ia32_misc_enable_msr;
@@ -400,7 +401,6 @@ struct kvm_arch{
struct hlist_head irq_ack_notifier_list;
int vapics_in_nmi_mode;

- int round_robin_prev_vcpu;
unsigned int tss_addr;
struct page *apic_access_page;

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 998862a..814466f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -338,8 +338,9 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
struct kvm_vcpu *vcpu = apic->vcpu;

switch (delivery_mode) {
- case APIC_DM_FIXED:
case APIC_DM_LOWEST:
+ vcpu->arch.apic_arb_prio++;
+ case APIC_DM_FIXED:
/* FIXME add logic for vcpu on reset */
if (unlikely(!apic_enabled(apic)))
break;
@@ -416,43 +417,9 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
return result;
}

-static struct kvm_lapic *kvm_apic_round_robin(struct kvm *kvm, u8 vector,
- unsigned long *bitmap)
+int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
{
- int last;
- int next;
- struct kvm_lapic *apic = NULL;
-
- last = kvm->arch.round_robin_prev_vcpu;
- next = last;
-
- do {
- if (++next == KVM_MAX_VCPUS)
- next = 0;
- if (kvm->vcpus[next] == NULL || !test_bit(next, bitmap))
- continue;
- apic = kvm->vcpus[next]->arch.apic;
- if (apic && apic_enabled(apic))
- break;
- apic = NULL;
- } while (next != last);
- kvm->arch.round_robin_prev_vcpu = next;
-
- if (!apic)
- printk(KERN_DEBUG "vcpu not ready for apic_round_robin\n");
-
- return apic;
-}
-
-struct kvm_vcpu *kvm_get_lowest_prio_vcpu(struct kvm *kvm, u8 vector,
- unsigned long *bitmap)
-{
- struct kvm_lapic *apic;
-
- apic = kvm_apic_round_robin(kvm, vector, bitmap);
- if (apic)
- return apic->vcpu;
- return NULL;
+ return vcpu1->arch.apic_arb_prio - vcpu2->arch.apic_arb_prio;
}

static void apic_set_eoi(struct kvm_lapic *apic)
@@ -908,6 +875,8 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
vcpu->arch.apic_base |= MSR_IA32_APICBASE_BSP;
apic_update_ppr(apic);

+ vcpu->arch.apic_arb_prio = 0;
+
apic_debug(KERN_INFO "%s: vcpu=%p, id=%d, base_msr="
"0x%016" PRIx64 ", base_address=0x%0lx.\n", __func__,
vcpu, kvm_apic_id(apic),
diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index d996c7a..e7bc92d 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -64,10 +64,9 @@ static inline struct kvm_ioapic *ioapic_irqchip(struct kvm *kvm)
return kvm->arch.vioapic;
}

-struct kvm_vcpu *kvm_get_lowest_prio_vcpu(struct kvm *kvm, u8 vector,
- unsigned long *bitmap);
int kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
int short_hand, int dest, int dest_mode);
+int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2);
void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode);
int kvm_ioapic_init(struct kvm *kvm);
int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index e43701c..f5e059b 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -47,7 +47,7 @@ void kvm_get_intr_delivery_bitmask(struct kvm *kvm, struct kvm_lapic *src,
int dest_id, int dest_mode, bool low_prio, int short_hand,
unsigned long *deliver_bitmask)
{
- int i;
+ int i, lowest = -1;
struct kvm_vcpu *vcpu;

if (dest_mode == 0 && dest_id == 0xff && low_prio)
@@ -64,15 +64,18 @@ void kvm_get_intr_delivery_bitmask(struct kvm *kvm, struct kvm_lapic *src,
dest_mode))
continue;

- __set_bit(i, deliver_bitmask);
+ if (!low_prio) {
+ __set_bit(i, deliver_bitmask);
+ } else {
+ if (lowest < 0)
+ lowest = i;
+ if (kvm_apic_compare_prio(vcpu, kvm->vcpus[lowest]) < 0)
+ lowest = i;
+ }
}

- if (low_prio) {
- vcpu = kvm_get_lowest_prio_vcpu(kvm, 0, deliver_bitmask);
- bitmap_zero(deliver_bitmask, KVM_MAX_VCPUS);
- if (vcpu)
- __set_bit(vcpu->vcpu_id, deliver_bitmask);
- }
+ if (lowest != -1)
+ __set_bit(lowest, deliver_bitmask);
}

static int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
--
1.6.0.6


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