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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.7] arm: read/write rank->vcpu atomically
commit 9d9be1eaaae3e8cf40debe360ddb98242ab34f25
Author: Stefano Stabellini <sstabellini@xxxxxxxxxx>
AuthorDate: Fri Mar 17 12:23:57 2017 -0700
Commit: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Fri Mar 17 12:23:57 2017 -0700
arm: read/write rank->vcpu atomically
We don't need a lock in vgic_get_target_vcpu anymore, solving the
following lock inversion bug: the rank lock should be taken first, then
the vgic lock. However, gic_update_one_lr is called with the vgic lock
held, and it calls vgic_get_target_vcpu, which tries to obtain the rank
lock.
Coverity-ID: 1381855
Coverity-ID: 1381853
Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
---
xen/arch/arm/vgic-v2.c | 6 +++---
xen/arch/arm/vgic-v3.c | 6 +++---
xen/arch/arm/vgic.c | 27 +++++----------------------
xen/include/asm-arm/vgic.h | 4 +++-
4 files changed, 14 insertions(+), 29 deletions(-)
diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index 9adb4a9..38916a0 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -79,7 +79,7 @@ static uint32_t vgic_fetch_itargetsr(struct vgic_irq_rank
*rank,
offset &= ~(NR_TARGETS_PER_ITARGETSR - 1);
for ( i = 0; i < NR_TARGETS_PER_ITARGETSR; i++, offset++ )
- reg |= (1 << rank->vcpu[offset]) << (i * NR_BITS_PER_TARGET);
+ reg |= (1 << read_atomic(&rank->vcpu[offset])) << (i *
NR_BITS_PER_TARGET);
return reg;
}
@@ -152,7 +152,7 @@ static void vgic_store_itargetsr(struct domain *d, struct
vgic_irq_rank *rank,
/* The vCPU ID always starts from 0 */
new_target--;
- old_target = rank->vcpu[offset];
+ old_target = read_atomic(&rank->vcpu[offset]);
/* Only migrate the vIRQ if the target vCPU has changed */
if ( new_target != old_target )
@@ -162,7 +162,7 @@ static void vgic_store_itargetsr(struct domain *d, struct
vgic_irq_rank *rank,
virq);
}
- rank->vcpu[offset] = new_target;
+ write_atomic(&rank->vcpu[offset], new_target);
}
}
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index b37a7c0..dac0e4a 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -107,7 +107,7 @@ static uint64_t vgic_fetch_irouter(struct vgic_irq_rank
*rank,
/* Get the index in the rank */
offset &= INTERRUPT_RANK_MASK;
- return vcpuid_to_vaffinity(rank->vcpu[offset]);
+ return vcpuid_to_vaffinity(read_atomic(&rank->vcpu[offset]));
}
/*
@@ -135,7 +135,7 @@ static void vgic_store_irouter(struct domain *d, struct
vgic_irq_rank *rank,
offset &= virq & INTERRUPT_RANK_MASK;
new_vcpu = vgic_v3_irouter_to_vcpu(d, irouter);
- old_vcpu = d->vcpu[rank->vcpu[offset]];
+ old_vcpu = d->vcpu[read_atomic(&rank->vcpu[offset])];
/*
* From the spec (see 8.9.13 in IHI 0069A), any write with an
@@ -153,7 +153,7 @@ static void vgic_store_irouter(struct domain *d, struct
vgic_irq_rank *rank,
if ( new_vcpu != old_vcpu )
vgic_migrate_irq(old_vcpu, new_vcpu, virq);
- rank->vcpu[offset] = new_vcpu->vcpu_id;
+ write_atomic(&rank->vcpu[offset], new_vcpu->vcpu_id);
}
static inline bool vgic_reg64_check_access(struct hsr_dabt dabt)
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 413ff16..07902c1 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -87,7 +87,7 @@ static void vgic_rank_init(struct vgic_irq_rank *rank,
uint8_t index,
rank->index = index;
for ( i = 0; i < NR_INTERRUPT_PER_RANK; i++ )
- rank->vcpu[i] = vcpu;
+ write_atomic(&rank->vcpu[i], vcpu);
}
int domain_vgic_init(struct domain *d, unsigned int nr_spis)
@@ -214,28 +214,11 @@ int vcpu_vgic_free(struct vcpu *v)
return 0;
}
-/* The function should be called by rank lock taken. */
-static struct vcpu *__vgic_get_target_vcpu(struct vcpu *v, unsigned int virq)
-{
- struct vgic_irq_rank *rank = vgic_rank_irq(v, virq);
-
- ASSERT(spin_is_locked(&rank->lock));
-
- return v->domain->vcpu[rank->vcpu[virq & INTERRUPT_RANK_MASK]];
-}
-
-/* takes the rank lock */
struct vcpu *vgic_get_target_vcpu(struct vcpu *v, unsigned int virq)
{
- struct vcpu *v_target;
struct vgic_irq_rank *rank = vgic_rank_irq(v, virq);
- unsigned long flags;
-
- vgic_lock_rank(v, rank, flags);
- v_target = __vgic_get_target_vcpu(v, virq);
- vgic_unlock_rank(v, rank, flags);
-
- return v_target;
+ int target = read_atomic(&rank->vcpu[virq & INTERRUPT_RANK_MASK]);
+ return v->domain->vcpu[target];
}
static int vgic_get_virq_priority(struct vcpu *v, unsigned int virq)
@@ -322,7 +305,7 @@ void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
while ( (i = find_next_bit(&mask, 32, i)) < 32 ) {
irq = i + (32 * n);
- v_target = __vgic_get_target_vcpu(v, irq);
+ v_target = vgic_get_target_vcpu(v, irq);
p = irq_to_pending(v_target, irq);
clear_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
gic_remove_from_queues(v_target, irq);
@@ -360,7 +343,7 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
}
}
- v_target = __vgic_get_target_vcpu(v, irq);
+ v_target = vgic_get_target_vcpu(v, irq);
p = irq_to_pending(v_target, irq);
set_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
spin_lock_irqsave(&v_target->arch.vgic.lock, flags);
diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
index de192d0..98932e7 100644
--- a/xen/include/asm-arm/vgic.h
+++ b/xen/include/asm-arm/vgic.h
@@ -107,7 +107,9 @@ struct vgic_irq_rank {
/*
* It's more convenient to store a target VCPU per vIRQ
- * than the register ITARGETSR/IROUTER itself
+ * than the register ITARGETSR/IROUTER itself.
+ * Use atomic operations to read/write the vcpu fields to avoid
+ * taking the rank lock.
*/
uint8_t vcpu[32];
};
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7
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