[RFC PATCH v3 8/9] kvm,vmx: Add atomic synchronization with CPU Hotplug

From: Srivatsa S. Bhat
Date: Fri Dec 07 2012 - 12:41:30 EST


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() in vmx_vcpu_load() to prevent CPUs from
going offline while clearing vmcs.

Reported-by: Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx>
Debugged-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---

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..d8a4cf1 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();
loaded_vmcs_clear(vmx->loaded_vmcs);
+ put_online_cpus_atomic();
+ }

if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/