1 From a6a711f3db1b4c64f214c3844adf9da3caa0dc61 Mon Sep 17 00:00:00 2001
2 From: Paul Mackerras <paulus@ozlabs.org>
3 Date: Thu, 23 May 2019 16:36:32 +1000
4 Subject: KVM: PPC: Book3S HV: Don't take kvm->lock around kvm_for_each_vcpu
6 Content-Type: text/plain; charset=UTF-8
7 Content-Transfer-Encoding: 8bit
9 [ Upstream commit 5a3f49364c3ffa1107bd88f8292406e98c5d206c ]
11 Currently the HV KVM code takes the kvm->lock around calls to
12 kvm_for_each_vcpu() and kvm_get_vcpu_by_id() (which can call
13 kvm_for_each_vcpu() internally). However, that leads to a lock
14 order inversion problem, because these are called in contexts where
15 the vcpu mutex is held, but the vcpu mutexes nest within kvm->lock
16 according to Documentation/virtual/kvm/locking.txt. Hence there
17 is a possibility of deadlock.
19 To fix this, we simply don't take the kvm->lock mutex around these
20 calls. This is safe because the implementations of kvm_for_each_vcpu()
21 and kvm_get_vcpu_by_id() have been designed to be able to be called
24 Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
25 Reviewed-by: Cédric Le Goater <clg@kaod.org>
26 Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
27 Signed-off-by: Sasha Levin <sashal@kernel.org>
29 arch/powerpc/kvm/book3s_hv.c | 9 +--------
30 1 file changed, 1 insertion(+), 8 deletions(-)
32 diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
33 index 58746328b9bd..3b7488fce3db 100644
34 --- a/arch/powerpc/kvm/book3s_hv.c
35 +++ b/arch/powerpc/kvm/book3s_hv.c
36 @@ -392,12 +392,7 @@ static void kvmppc_dump_regs(struct kvm_vcpu *vcpu)
38 static struct kvm_vcpu *kvmppc_find_vcpu(struct kvm *kvm, int id)
40 - struct kvm_vcpu *ret;
42 - mutex_lock(&kvm->lock);
43 - ret = kvm_get_vcpu_by_id(kvm, id);
44 - mutex_unlock(&kvm->lock);
46 + return kvm_get_vcpu_by_id(kvm, id);
49 static void init_vpa(struct kvm_vcpu *vcpu, struct lppaca *vpa)
50 @@ -1258,7 +1253,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
51 struct kvmppc_vcore *vc = vcpu->arch.vcore;
54 - mutex_lock(&kvm->lock);
57 * If ILE (interrupt little-endian) has changed, update the
58 @@ -1298,7 +1292,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
60 vc->lpcr = (vc->lpcr & ~mask) | (new_lpcr & mask);
61 spin_unlock(&vc->lock);
62 - mutex_unlock(&kvm->lock);
65 static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,