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    SubjectRe: [PATCH v3 00/11] KVM: nVMX: Fixes for nested state migration when eVMCS is in use
    Date
    Vitaly Kuznetsov <vkuznets@redhat.com> writes:

    > Changes since v2:
    > - 'KVM: nVMX: Use '-1' in 'hv_evmcs_vmptr' to indicate that eVMCS is not in
    > use'/ 'KVM: nVMX: Introduce 'EVMPTR_MAP_PENDING' post-migration state'
    > patches instead of 'KVM: nVMX: Introduce nested_evmcs_is_used()' [Paolo]
    > - 'KVM: nVMX: Don't set 'dirty_vmcs12' flag on enlightened VMPTRLD' patch
    > added [Max]
    > - 'KVM: nVMX: Release eVMCS when enlightened VMENTRY was disabled' patch
    > added.
    > - 'KVM: nVMX: Make copy_vmcs12_to_enlightened()/copy_enlightened_to_vmcs12()
    > return 'void'' patch added [Paolo]
    > - R-b tags added [Max]
    >
    > Original description:
    >
    > Commit f5c7e8425f18 ("KVM: nVMX: Always make an attempt to map eVMCS after
    > migration") fixed the most obvious reason why Hyper-V on KVM (e.g. Win10
    > + WSL2) was crashing immediately after migration. It was also reported
    > that we have more issues to fix as, while the failure rate was lowered
    > signifincatly, it was still possible to observe crashes after several
    > dozens of migration. Turns out, the issue arises when we manage to issue
    > KVM_GET_NESTED_STATE right after L2->L2 VMEXIT but before L1 gets a chance
    > to run. This state is tracked with 'need_vmcs12_to_shadow_sync' flag but
    > the flag itself is not part of saved nested state. A few other less
    > significant issues are fixed along the way.
    >
    > While there's no proof this series fixes all eVMCS related problems,
    > Win10+WSL2 was able to survive 3333 (thanks, Max!) migrations without
    > crashing in testing.
    >
    > Patches are based on the current kvm/next tree.

    Paolo, Max,

    Just to double-check: are we good here? I know there are more
    improvements/ideas to explore but I'd like to treat this patchset as a
    set of fixes, it would be unfortunate if we miss 5.14.

    --
    Vitaly

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