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| author | pingfan liu <qemulist@gmail.com> | 2013-11-15 16:35:00 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-01-09 12:24:19 -0800 |
| commit | 56046f38a4ef578303487009c58e2f86fab7aaea (patch) | |
| tree | 50c1146aa89d8de606b7609b542efc9052cb7c2c /arch | |
| parent | d58dd25632be5ec0250630ccddfea7e9bd913ecb (diff) | |
| download | lwn-56046f38a4ef578303487009c58e2f86fab7aaea.tar.gz lwn-56046f38a4ef578303487009c58e2f86fab7aaea.zip | |
powerpc: kvm: fix rare but potential deadlock scene
commit 91648ec09c1ef69c4d840ab6dab391bfb452d554 upstream.
Since kvmppc_hv_find_lock_hpte() is called from both virtmode and
realmode, so it can trigger the deadlock.
Suppose the following scene:
Two physical cpuM, cpuN, two VM instances A, B, each VM has a group of
vcpus.
If on cpuM, vcpu_A_1 holds bitlock X (HPTE_V_HVLOCK), then is switched
out, and on cpuN, vcpu_A_2 try to lock X in realmode, then cpuN will be
caught in realmode for a long time.
What makes things even worse if the following happens,
On cpuM, bitlockX is hold, on cpuN, Y is hold.
vcpu_B_2 try to lock Y on cpuM in realmode
vcpu_A_2 try to lock X on cpuN in realmode
Oops! deadlock happens
Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
Reviewed-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/kvm/book3s_64_mmu_hv.c | 6 | ||||
| -rw-r--r-- | arch/powerpc/kvm/book3s_hv_rm_mmu.c | 4 |
2 files changed, 9 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 5880dfb31074..b616e364dbe9 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -473,11 +473,14 @@ static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, slb_v = vcpu->kvm->arch.vrma_slb_v; } + preempt_disable(); /* Find the HPTE in the hash table */ index = kvmppc_hv_find_lock_hpte(kvm, eaddr, slb_v, HPTE_V_VALID | HPTE_V_ABSENT); - if (index < 0) + if (index < 0) { + preempt_enable(); return -ENOENT; + } hptep = (unsigned long *)(kvm->arch.hpt_virt + (index << 4)); v = hptep[0] & ~HPTE_V_HVLOCK; gr = kvm->arch.revmap[index].guest_rpte; @@ -485,6 +488,7 @@ static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, /* Unlock the HPTE */ asm volatile("lwsync" : : : "memory"); hptep[0] = v; + preempt_enable(); gpte->eaddr = eaddr; gpte->vpage = ((v & HPTE_V_AVPN) << 4) | ((eaddr >> 12) & 0xfff); diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c index 6dcbb49105a4..049b899e40e4 100644 --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c @@ -724,6 +724,10 @@ static int slb_base_page_shift[4] = { 20, /* 1M, unsupported */ }; +/* When called from virtmode, this func should be protected by + * preempt_disable(), otherwise, the holding of HPTE_V_HVLOCK + * can trigger deadlock issue. + */ long kvmppc_hv_find_lock_hpte(struct kvm *kvm, gva_t eaddr, unsigned long slb_v, unsigned long valid) { |