CVE-2026-89930

In the Linux kernel, the following vulnerability has been resolved:

KVM: nVMX: Service local TLB flushes on failed nested VM-Enter

KVM services local TLB flushes on "full" nested VM-Exits (through

__nested_vmx_vmexit()), but not if a nested VM-Enter fails (e.g. due to

failed VMCS checks in nested_vmx_enter_non_root_mode()).

However, it is possible that KVM had queued TLB flushes that need to be

performed, even if the nested VM-Enter was not successful. For example,

if VPID is disabled for L2 (via nested_vmx_transition_tlb_flush(), or if

via the MSR load lists, as the SDM says:

If any MSR is being loaded in such a way that would architecturally

require a TLB flush, the TLBs are updated so that, after VM entry, the

logical processor will not use any translations that were cached before

the transition.

The SDM is unclear about when the TLB flush should occur, and whether or

not a failed VM entry would flush the TLB, so it is safer to always

do the TLB flush in this case.

More concretely, KVM also updates the last VPID L1 used for L2 in

nested_vmx_transition_tlb_flush() (i.e. last_vpid), even if the VM entry

ultimately fails. With the current code, KVM could miss a TLB flush if

L1 changes L2's VPID, then does a failed VM entry followed by a

successful one, as the failed VM entry would update last_vpid but not

actually flush the TLB. Servicing local TLB flushes on failed VM entries

makes sure that the TLB is always flushed when last_vpid is updated.