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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2012-11-28 07:54:14 -0500
committerMarcelo Tosatti <mtosatti@redhat.com>2012-11-29 18:14:46 -0500
commit5a560f8b5ed361c7be783d5a671ea26ca4d6fa01 (patch)
treeec3e4aa913bcdc0f97222f7a9ee4b52104d1ed1f /arch/x86/kvm/vmx.c
parente6c7d32172f10b68fa9a3be05aa1231352a52171 (diff)
KVM: VMX: fix memory order between loading vmcs and clearing vmcs
vmcs->cpu indicates whether it exists on the target cpu, -1 means the vmcs does not exist on any vcpu If vcpu load vmcs with vmcs.cpu = -1, it can be directly added to cpu's percpu list. The list can be corrupted if the cpu prefetch the vmcs's list before reading vmcs->cpu. Meanwhile, we should remove vmcs from the list before making vmcs->vcpu == -1 be visible Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx.c')
-rw-r--r--arch/x86/kvm/vmx.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4406374e3b6d..3606154bbc8b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1002,6 +1002,15 @@ static void __loaded_vmcs_clear(void *arg)
1002 if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs) 1002 if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs)
1003 per_cpu(current_vmcs, cpu) = NULL; 1003 per_cpu(current_vmcs, cpu) = NULL;
1004 list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link); 1004 list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link);
1005
1006 /*
1007 * we should ensure updating loaded_vmcs->loaded_vmcss_on_cpu_link
1008 * is before setting loaded_vmcs->vcpu to -1 which is done in
1009 * loaded_vmcs_init. Otherwise, other cpu can see vcpu = -1 fist
1010 * then adds the vmcs into percpu list before it is deleted.
1011 */
1012 smp_wmb();
1013
1005 loaded_vmcs_init(loaded_vmcs); 1014 loaded_vmcs_init(loaded_vmcs);
1006} 1015}
1007 1016
@@ -1537,6 +1546,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
1537 1546
1538 kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); 1547 kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
1539 local_irq_disable(); 1548 local_irq_disable();
1549
1550 /*
1551 * Read loaded_vmcs->cpu should be before fetching
1552 * loaded_vmcs->loaded_vmcss_on_cpu_link.
1553 * See the comments in __loaded_vmcs_clear().
1554 */
1555 smp_rmb();
1556
1540 list_add(&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link, 1557 list_add(&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link,
1541 &per_cpu(loaded_vmcss_on_cpu, cpu)); 1558 &per_cpu(loaded_vmcss_on_cpu, cpu));
1542 local_irq_enable(); 1559 local_irq_enable();