[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 _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx https://lists.xenproject.org/xen-changelog
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