[PATCH v2 02/13] KVM: x86: add kvm_apic_map_get_dest_lapic

Radim Krčmář
2016-07-07T17:15:39Z

kvm_irq_delivery_to_apic_fast and kvm_intr_is_single_vcpu_fast both
compute the interrupt destination. Factor the code.

'struct kvm_lapic **dst = NULL' had to be added to silence GCC.
GCC might complain about potential NULL access in the future, because it
missed conditions that avoided uninitialized uses of dst.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
v2: do not point to out-of-scope value (return &src) [Paolo]

arch/x86/kvm/lapic.c | 242 ++++++++++++++++++++++-----------------------------
1 file changed, 104 insertions(+), 138 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 22a6474af220..2987843657db 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -671,14 +671,99 @@ static void kvm_apic_disabled_lapic_found(struct kvm *kvm)
}
}

+/* Return true if the interrupt can be handled by using *bitmap as index mask
+ * for valid destinations in *dst array.
+ * Return false if kvm_apic_map_get_dest_lapic did nothing useful.
+ * Note: we may have zero kvm_lapic destinations when we return true, which
+ * means that the interrupt should be dropped. In this case, *bitmap would be
+ * zero and *dst undefined.
+ */
+static inline bool kvm_apic_map_get_dest_lapic(struct kvm *kvm,
+ struct kvm_lapic **src, struct kvm_lapic_irq *irq,
+ struct kvm_apic_map *map, struct kvm_lapic ***dst,
+ unsigned long *bitmap)
+{
+ int i, lowest;
+ bool x2apic_ipi;
+ u16 cid;
+
+ if (irq->shorthand == APIC_DEST_SELF && src) {
+ *dst = src;
+ *bitmap = 1;
+ return true;
+ } else if (irq->shorthand)
+ return false;
+
+ x2apic_ipi = src && *src && apic_x2apic_mode(*src);
+ if (irq->dest_id == (x2apic_ipi ? X2APIC_BROADCAST : APIC_BROADCAST))
+ return false;
+
+ if (!map)
+ return false;
+
+ if (irq->dest_mode == APIC_DEST_PHYSICAL) {
+ if (irq->dest_id >= ARRAY_SIZE(map->phys_map)) {
+ *bitmap = 0;
+ } else {
+ *dst = &map->phys_map[irq->dest_id];
+ *bitmap = 1;
+ }
+ return true;
+ }
+
+ if (!kvm_apic_logical_map_valid(map))
+ return false;
+
+ apic_logical_id(map, irq->dest_id, &cid, (u16 *)bitmap);
+
+ if (cid >= ARRAY_SIZE(map->logical_map)) {
+ *bitmap = 0;
+ return true;
+ }
+
+ *dst = map->logical_map[cid];
+
+ if (!kvm_lowest_prio_delivery(irq))
+ return true;
+
+ if (!kvm_vector_hashing_enabled()) {
+ lowest = -1;
+ for_each_set_bit(i, bitmap, 16) {
+ if (!(*dst)[i])
+ continue;
+ if (lowest < 0)
+ lowest = i;
+ else if (kvm_apic_compare_prio((*dst)[i]->vcpu,
+ (*dst)[lowest]->vcpu) < 0)
+ lowest = i;
+ }
+ } else {
+ if (!*bitmap)
+ return true;
+
+ lowest = kvm_vector_to_index(irq->vector, hweight16(*bitmap),
+ bitmap, 16);
+
+ if (!(*dst)[lowest]) {
+ kvm_apic_disabled_lapic_found(kvm);
+ *bitmap = 0;
+ return true;
+ }
+ }
+
+ *bitmap = (lowest >= 0) ? 1 << lowest : 0;
+
+ return true;
+}
+
bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq, int *r, struct dest_map *dest_map)
{
struct kvm_apic_map *map;
- unsigned long bitmap = 1;
- struct kvm_lapic **dst;
+ unsigned long bitmap;
+ struct kvm_lapic **dst = NULL;
int i;
- bool ret, x2apic_ipi;
+ bool ret;

*r = -1;

@@ -687,86 +772,19 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
return true;
}

- if (irq->shorthand)
- return false;
-
- x2apic_ipi = src && apic_x2apic_mode(src);
- if (irq->dest_id == (x2apic_ipi ? X2APIC_BROADCAST : APIC_BROADCAST))
- return false;
-
- ret = true;
rcu_read_lock();
map = rcu_dereference(kvm->arch.apic_map);

- if (!map) {
- ret = false;
- goto out;
- }
-
- if (irq->dest_mode == APIC_DEST_PHYSICAL) {
- if (irq->dest_id >= ARRAY_SIZE(map->phys_map))
- goto out;
-
- dst = &map->phys_map[irq->dest_id];
- } else {
- u16 cid;
-
- if (!kvm_apic_logical_map_valid(map)) {
- ret = false;
- goto out;
+ ret = kvm_apic_map_get_dest_lapic(kvm, &src, irq, map, &dst, &bitmap);
+ if (ret)
+ for_each_set_bit(i, &bitmap, 16) {
+ if (!dst[i])
+ continue;
+ if (*r < 0)
+ *r = 0;
+ *r += kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
}

- apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap);
-
- if (cid >= ARRAY_SIZE(map->logical_map))
- goto out;
-
- dst = map->logical_map[cid];
-
- if (!kvm_lowest_prio_delivery(irq))
- goto set_irq;
-
- if (!kvm_vector_hashing_enabled()) {
- int l = -1;
- for_each_set_bit(i, &bitmap, 16) {
- if (!dst[i])
- continue;
- if (l < 0)
- l = i;
- else if (kvm_apic_compare_prio(dst[i]->vcpu,
- dst[l]->vcpu) < 0)
- l = i;
- }
- bitmap = (l >= 0) ? 1 << l : 0;
- } else {
- int idx;
- unsigned int dest_vcpus;
-
- dest_vcpus = hweight16(bitmap);
- if (dest_vcpus == 0)
- goto out;
-
- idx = kvm_vector_to_index(irq->vector,
- dest_vcpus, &bitmap, 16);
-
- if (!dst[idx]) {
- kvm_apic_disabled_lapic_found(kvm);
- goto out;
- }
-
- bitmap = (idx >= 0) ? 1 << idx : 0;
- }
- }
-
-set_irq:
- for_each_set_bit(i, &bitmap, 16) {
- if (!dst[i])
- continue;
- if (*r < 0)
- *r = 0;
- *r += kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
- }
-out:
rcu_read_unlock();
return ret;
}
@@ -789,8 +807,9 @@ bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
struct kvm_vcpu **dest_vcpu)
{
struct kvm_apic_map *map;
+ unsigned long bitmap;
+ struct kvm_lapic **dst = NULL;
bool ret = false;
- struct kvm_lapic *dst = NULL;

if (irq->shorthand)
return false;
@@ -798,69 +817,16 @@ bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
rcu_read_lock();
map = rcu_dereference(kvm->arch.apic_map);

- if (!map)
- goto out;
+ if (kvm_apic_map_get_dest_lapic(kvm, NULL, irq, map, &dst, &bitmap) &&
+ hweight16(bitmap) == 1) {
+ unsigned long i = find_first_bit(&bitmap, 16);

- if (irq->dest_mode == APIC_DEST_PHYSICAL) {
- if (irq->dest_id == 0xFF)
- goto out;
-
- if (irq->dest_id >= ARRAY_SIZE(map->phys_map))
- goto out;
-
- dst = map->phys_map[irq->dest_id];
- if (dst && kvm_apic_present(dst->vcpu))
- *dest_vcpu = dst->vcpu;
- else
- goto out;
- } else {
- u16 cid;
- unsigned long bitmap = 1;
- int i, r = 0;
-
- if (!kvm_apic_logical_map_valid(map))
- goto out;
-
- apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap);
-
- if (cid >= ARRAY_SIZE(map->logical_map))
- goto out;
-
- if (kvm_vector_hashing_enabled() &&
- kvm_lowest_prio_delivery(irq)) {
- int idx;
- unsigned int dest_vcpus;
-
- dest_vcpus = hweight16(bitmap);
- if (dest_vcpus == 0)
- goto out;
-
- idx = kvm_vector_to_index(irq->vector, dest_vcpus,
- &bitmap, 16);
-
- dst = map->logical_map[cid][idx];
- if (!dst) {
- kvm_apic_disabled_lapic_found(kvm);
- goto out;
- }
-
- *dest_vcpu = dst->vcpu;
- } else {
- for_each_set_bit(i, &bitmap, 16) {
- dst = map->logical_map[cid][i];
- if (++r == 2)
- goto out;
- }
-
- if (dst && kvm_apic_present(dst->vcpu))
- *dest_vcpu = dst->vcpu;
- else
- goto out;
+ if (dst[i]) {
+ *dest_vcpu = dst[i]->vcpu;
+ ret = true;
}
}

- ret = true;
-out:
rcu_read_unlock();
return ret;
}
--
2.9.0