preempt_disable() will no longer help prevent CPUs from going offline, once
stop_machine() gets removed from the CPU offline path. So use
get/put_online_cpus_atomic_full() in vmx_vcpu_load() to prevent CPUs from
going offline while clearing vmcs. Here we truly need full-synchronization
with CPU hotplug (and not just an unchanging cpu_online_mask), because we
want to prevent race with the CPU_DYING callback from kvm.
Reported-by: Michael Wang <wang...@linux.vnet.ibm.com>
Debugged-by: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com>
---
arch/x86/kvm/vmx.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f858159..23c1063 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1519,10 +1519,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int
cpu)
struct vcpu_vmx *vmx = to_vmx(vcpu);
u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
- if (!vmm_exclusive)
+ if (!vmm_exclusive) {
kvm_cpu_vmxon(phys_addr);
- else if (vmx->loaded_vmcs->cpu != cpu)
+ } else if (vmx->loaded_vmcs->cpu != cpu) {
+ /* Prevent any CPU from going offline */
+ get_online_cpus_atomic_full();
loaded_vmcs_clear(vmx->loaded_vmcs);
+ put_online_cpus_atomic_full();
+ }
if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;
--
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