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authorpingfan liu <qemulist@gmail.com>2013-11-15 16:35:00 +0800
committerAlexander Graf <agraf@suse.de>2013-11-18 22:41:57 +0100
commit91648ec09c1ef69c4d840ab6dab391bfb452d554 (patch)
tree05cb5c7b284901e91984039244298094a3e3604d /arch/powerpc/kvm/book3s_hv_rm_mmu.c
parentc9438092cae4a5bdbd146ca1385e85dcd6e847f8 (diff)
powerpc: kvm: fix rare but potential deadlock scene
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> CC: stable@vger.kernel.org Signed-off-by: Alexander Graf <agraf@suse.de>
Diffstat (limited to 'arch/powerpc/kvm/book3s_hv_rm_mmu.c')
-rw-r--r--arch/powerpc/kvm/book3s_hv_rm_mmu.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index fddbf989f37e..1931aa341a72 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -749,6 +749,10 @@ 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)
{

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