In VMX, before we bring down a CPU we must VMCLEAR all VMCSs loaded on it because (at least in theory) the processor might not have written all of its content back to memory. Since a patch from June 26, 2008, this is done using a per-cpu "vcpus_on_cpu" linked list of vcpus loaded on each CPU. The problem is that with nested VMX, we no longer have the concept of a vcpu being loaded on a cpu: A vcpu has multiple VMCSs (one for L1, others for each L2), and each of those may be have been last loaded on a different cpu. This trivial patch changes the code to keep on vcpus_on_cpu only L1 VMCSs. This fixes crashes on L1 shutdown caused by incorrectly maintaing the linked lists. It is not a complete solution, though. It doesn't flush the inactive L1 or L2 VMCSs loaded on a CPU which is being shutdown. Doing this correctly will probably require replacing the vcpu linked list by a link list of "saved_vcms" objects (VMCS, cpu and launched), and it is left as a TODO. Signed-off-by: Nadav Har'El <nyh@xxxxxxxxxx> --- arch/x86/kvm/vmx.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) --- .before/arch/x86/kvm/vmx.c 2011-05-08 10:43:18.000000000 +0300 +++ .after/arch/x86/kvm/vmx.c 2011-05-08 10:43:18.000000000 +0300 @@ -638,7 +638,9 @@ static void __vcpu_clear(void *arg) vmcs_clear(vmx->vmcs); if (per_cpu(current_vmcs, cpu) == vmx->vmcs) per_cpu(current_vmcs, cpu) = NULL; - list_del(&vmx->local_vcpus_link); + /* TODO: currently, local_vcpus_link is just for L1 VMCSs */ + if (!is_guest_mode(&vmx->vcpu)) + list_del(&vmx->local_vcpus_link); vmx->vcpu.cpu = -1; vmx->launched = 0; } @@ -1100,8 +1102,10 @@ static void vmx_vcpu_load(struct kvm_vcp kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); local_irq_disable(); - list_add(&vmx->local_vcpus_link, - &per_cpu(vcpus_on_cpu, cpu)); + /* TODO: currently, local_vcpus_link is just for L1 VMCSs */ + if (!is_guest_mode(&vmx->vcpu)) + list_add(&vmx->local_vcpus_link, + &per_cpu(vcpus_on_cpu, cpu)); local_irq_enable(); /* @@ -1806,7 +1810,9 @@ static void vmclear_local_vcpus(void) list_for_each_entry_safe(vmx, n, &per_cpu(vcpus_on_cpu, cpu), local_vcpus_link) - __vcpu_clear(vmx); + /* TODO: currently, local_vcpus_link is just for L1 VMCSs */ + if (!is_guest_mode(&vmx->vcpu)) + __vcpu_clear(vmx); } -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
