| Message ID | 20210503150854.1144255-1-vkuznets@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: nVMX: Fix migration of nested guests when eVMCS is in use | expand |
On 03/05/21 17:08, Vitaly Kuznetsov wrote: > Win10 guests with WSL2 enabled sometimes crash on migration when > enlightened VMCS was used. The condition seems to be induced by the > situation when L2->L1 exit is caused immediately after migration and > before L2 gets a chance to run (e.g. when there's an interrupt pending). Interesting, I think it gets to nested_vmx_vmexit before if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) { if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) { r = 0; goto out; } } due to the infamous calls to check_nested_events that are scattered through KVM? Paolo
Paolo Bonzini <pbonzini@redhat.com> writes: > On 03/05/21 17:08, Vitaly Kuznetsov wrote: >> Win10 guests with WSL2 enabled sometimes crash on migration when >> enlightened VMCS was used. The condition seems to be induced by the >> situation when L2->L1 exit is caused immediately after migration and >> before L2 gets a chance to run (e.g. when there's an interrupt pending). > > Interesting, I think it gets to nested_vmx_vmexit before > > if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) { > if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) { > r = 0; > goto out; > } > } > > due to the infamous calls to check_nested_events that are scattered > through KVM? Yea, vcpu_run() -> kvm_vcpu_running() -> vmx_check_nested_events() if I remember it correctly.
Win10 guests with WSL2 enabled sometimes crash on migration when enlightened VMCS was used. The condition seems to be induced by the situation when L2->L1 exit is caused immediately after migration and before L2 gets a chance to run (e.g. when there's an interrupt pending). The issue was introduced by commit f2c7ef3ba955 ("KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit") and the first patch of the series addresses the immediate issue. The eVMCS mapping restoration path, however, seems to be fragile and the rest of the series tries to make it more future proof by including eVMCS GPA in the migration data. Vitaly Kuznetsov (4): KVM: nVMX: Always make an attempt to map eVMCS after migration KVM: nVMX: Properly pad 'struct kvm_vmx_nested_state_hdr' KVM: nVMX: Introduce __nested_vmx_handle_enlightened_vmptrld() KVM: nVMX: Map enlightened VMCS upon restore when possible arch/x86/include/uapi/asm/kvm.h | 4 ++ arch/x86/kvm/vmx/nested.c | 82 +++++++++++++++++++++++---------- 2 files changed, 61 insertions(+), 25 deletions(-)