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authorpingfan liu <qemulist@gmail.com>2013-11-15 16:35:00 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-08 09:42:10 -0800
commit7898047084bed6716bbc2c08b969ddf364ca36fd (patch)
treef943653c9ab0acdb04b67ece6ae565cf5e35f339
parentbb4e90afb0b16996ff921762ab4212db0f40535f (diff)
downloadlinux-linaro-stable-7898047084bed6716bbc2c08b969ddf364ca36fd.tar.gz
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>
-rw-r--r--arch/powerpc/kvm/book3s_64_mmu_hv.c6
-rw-r--r--arch/powerpc/kvm/book3s_hv_rm_mmu.c4
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 c3beaeef3f60..87135be08687 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -393,11 +393,14 @@ 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;
@@ -405,6 +408,7 @@ 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 cec4daddbf31..eacf164eabb2 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -649,6 +649,10 @@ 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)
{