Commit b25820b9 authored by Paul Mackerras's avatar Paul Mackerras Committed by Greg Kroah-Hartman

KVM: PPC: Book3S HV: Don't take kvm->lock around kvm_for_each_vcpu

[ Upstream commit 5a3f4936 ]

Currently the HV KVM code takes the kvm->lock around calls to
kvm_for_each_vcpu() and kvm_get_vcpu_by_id() (which can call
kvm_for_each_vcpu() internally).  However, that leads to a lock
order inversion problem, because these are called in contexts where
the vcpu mutex is held, but the vcpu mutexes nest within kvm->lock
according to Documentation/virtual/kvm/locking.txt.  Hence there
is a possibility of deadlock.

To fix this, we simply don't take the kvm->lock mutex around these
calls.  This is safe because the implementations of kvm_for_each_vcpu()
and kvm_get_vcpu_by_id() have been designed to be able to be called
locklessly.
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Reviewed-by: default avatarCédric Le Goater <clg@kaod.org>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 9b3bd09b
...@@ -445,12 +445,7 @@ static void kvmppc_dump_regs(struct kvm_vcpu *vcpu) ...@@ -445,12 +445,7 @@ static void kvmppc_dump_regs(struct kvm_vcpu *vcpu)
static struct kvm_vcpu *kvmppc_find_vcpu(struct kvm *kvm, int id) static struct kvm_vcpu *kvmppc_find_vcpu(struct kvm *kvm, int id)
{ {
struct kvm_vcpu *ret; return kvm_get_vcpu_by_id(kvm, id);
mutex_lock(&kvm->lock);
ret = kvm_get_vcpu_by_id(kvm, id);
mutex_unlock(&kvm->lock);
return ret;
} }
static void init_vpa(struct kvm_vcpu *vcpu, struct lppaca *vpa) static void init_vpa(struct kvm_vcpu *vcpu, struct lppaca *vpa)
...@@ -1502,7 +1497,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr, ...@@ -1502,7 +1497,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
struct kvmppc_vcore *vc = vcpu->arch.vcore; struct kvmppc_vcore *vc = vcpu->arch.vcore;
u64 mask; u64 mask;
mutex_lock(&kvm->lock);
spin_lock(&vc->lock); spin_lock(&vc->lock);
/* /*
* If ILE (interrupt little-endian) has changed, update the * If ILE (interrupt little-endian) has changed, update the
...@@ -1542,7 +1536,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr, ...@@ -1542,7 +1536,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
mask &= 0xFFFFFFFF; mask &= 0xFFFFFFFF;
vc->lpcr = (vc->lpcr & ~mask) | (new_lpcr & mask); vc->lpcr = (vc->lpcr & ~mask) | (new_lpcr & mask);
spin_unlock(&vc->lock); spin_unlock(&vc->lock);
mutex_unlock(&kvm->lock);
} }
static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id, static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
......
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