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UPSTREAM: KVM: arm64: vgic: Don't acquire its_lock before config_lock

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commit f00327731131 ("KVM: arm64: Use config_lock to protect vgic
state") was meant to rectify a longstanding lock ordering issue in KVM
where the kvm->lock is taken while holding vcpu->mutex. As it so
happens, the aforementioned commit introduced yet another locking issue
by acquiring the its_lock before acquiring the config lock.

This is obviously wrong, especially considering that the lock ordering
is well documented in vgic.c. Reshuffle the locks once more to take the
config_lock before the its_lock. While at it, sprinkle in the lockdep
hinting that has become popular as of late to keep lockdep apprised of
our ordering.

Cc: stable@vger.kernel.org
Fixes: f00327731131 ("KVM: arm64: Use config_lock to protect vgic state")
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230412062733.988229-1-oliver.upton@linux.dev
(cherry picked from commit 49e5d16b6fc003407a33a9961b4bcbb970bd1c76)
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 278750073
Change-Id: If3a7d338bbcc490a7545ace0a8c039bb5e1dcbf0
This commit is contained in:
Oliver Upton 2023-04-12 06:27:33 +00:00 • committed by Will Deacon
parent b1bb8a0bc4
commit b5e26cd12f
1 changed files with 12 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

15
arch/arm64/kvm/vgic/vgic-its.c
View file

@ -1958,6 +1958,16 @@ static int vgic_its_create(struct kvm_device *dev, u32 type)
mutex_init(&its->its_lock);
mutex_init(&its->cmd_lock);
/* Yep, even more trickery for lock ordering... */
#ifdef CONFIG_LOCKDEP
mutex_lock(&dev->kvm->arch.config_lock);
mutex_lock(&its->cmd_lock);
mutex_lock(&its->its_lock);
mutex_unlock(&its->its_lock);
mutex_unlock(&its->cmd_lock);
mutex_unlock(&dev->kvm->arch.config_lock);
#endif
its->vgic_its_base = VGIC_ADDR_UNDEF;
INIT_LIST_HEAD(&its->device_list);
@ -2752,15 +2762,14 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
return 0;
mutex_lock(&kvm->lock);
mutex_lock(&its->its_lock);
if (!lock_all_vcpus(kvm)) {
mutex_unlock(&its->its_lock);
mutex_unlock(&kvm->lock);
return -EBUSY;
}
mutex_lock(&kvm->arch.config_lock);
mutex_lock(&its->its_lock);
switch (attr) {
case KVM_DEV_ARM_ITS_CTRL_RESET:
@ -2774,9 +2783,9 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
break;
}
mutex_unlock(&its->its_lock);
mutex_unlock(&kvm->arch.config_lock);
unlock_all_vcpus(kvm);
mutex_unlock(&its->its_lock);
mutex_unlock(&kvm->lock);
return ret;
}