On Mon, Oct 5, 2026 at 12:25 PM Mushahid Hussain <[email protected]> wrote: > > free_nested() frees vmcs02 but leaves need_sync_vmcs02_to_vmcs12_rare > set. The flag means that the rare guest fields of vmcs12 are valid > only in vmcs02. After vmcs02 is freed the flag is wrong. > > L1 then executes VMXON and loads a vmcs12 with VMPTRLD. The flag is > still set, so the first sync copies the rare fields from the new, > never launched vmcs02 into vmcs12. This sets TR, LDTR, GDTR, IDTR, > the segment registers and the FS/GS bases to zero in guest memory. > set_current_vmptr() re-arms the other lazy flags at VMPTRLD. This > flag has no such point, so VMXOFF is the place to clear it. > > A nested Hyper-V follows this sequence when it resumes from > hibernation. It executes VMXOFF before hibernation. On resume, it > reloads the VMCS images that winresume restored from the hiberfile. > VM-entry fails with exit reason 0x80000021 (invalid guest state) and > the guest hypervisor resets the machine. vmx_leave_nested() also goes > through free_nested(), so KVM_SET_NESTED_STATE takes the same path. > > Clear the flag together with the other nested state. > > Fixes: 7952d769c29c ("KVM: nVMX: Sync rarely accessed guest fields only when > needed") > Cc: [email protected] > Assisted-by: Claude:claude-fable-5.1 > Signed-off-by: Mushahid Hussain <[email protected]> Reviewed-by: Jim Mattson <[email protected]>
