Re: [PATCH v1 02/11] KVM: x86: add kvm_apic_map_get_dest_lapic

Paolo Bonzini
2016-07-01T07:58:27Z

On 30/06/2016 22:54, Radim Krčmář wrote:
> 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>
> ---
> v1: improved comment for kvm_apic_map_get_dest_lapic() [Peter]
>
> arch/x86/kvm/lapic.c | 241 ++++++++++++++++++++++-----------------------------
> 1 file changed, 103 insertions(+), 138 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 22a6474af220..238b87b068db 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -671,14 +671,98 @@ 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) {
> + *dst = &src;

This is not valid, &src dies as soon as you leave the function. You
need to pass &src into kvm_apic_map_get_dest_lapic and here do something
like

if (irq->shorthand) {
if (irq->shorthand == APIC_DEST_SELF && p_src) {
*dst = p_src;
*bitmap = 1;
return true;
}
return false;
}

If it's not too hard, I'd like to have patch 4 before this one.

Paolo

> + *bitmap = 1;
> + return true;
> + } else if (irq->shorthand)
> + return false;
> +
> + x2apic_ipi = 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 +771,19 @@ 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 +806,9 @@ 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 +816,16 @@ 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;
> }
>