CVE-2026-89929: KVM: nVM: Ensure INVVPID is emulated on the correct physical CPU
In the Linux kernel, the following vulnerability has been resolved:
KVM: nVM: Ensure INVVPID is emulated on the correct physical CPU
When emulating INVVPID, KVM executes INVVPID on the physical CPU using vpid02 (instead of the L1 assigned VPID), after doing some validations on the operands. However, it is possible that the physical CPU KVM executes INVVPID on is different from the CPU L2 is running on.
For example, in the following scenario: - L2 runs on CPU #1 and exits to L1 (vmx->nested.vmcs02.cpu=1) - L1 migrates to CPU #2 and executes INVVPID - KVM executes INVVPID on CPU #2 - L1 migrates back to CPU #1 and runs L2 (vmx->nested.vmcs02.cpu=1)
The TLB entries on CPU #1 are never invalidated, because INVVPID was executed on CPU #2, and vmcs02 never ran on a different pCPU (i.e. vmxvcpuloadvmcs() will not request KVMREQTLBFLUSH).
Ensure that INVVPID is being executed on the same pCPU that L2 last ran on, and if not, fallback to clearing lastvpid=0 to trigger a full VPID flush on the next nested VM-Enter (as KVM will detect L1 using a different VPID for L2). If L2 ends up running on a different pCPU, KVM will flush the TLB anyway through vmxvcpuloadvmcs().
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Linux kernel (KVM: nVM: Ensure INVVPID is emulated on the correct physical CPU)to a version that resolves this vulnerability.Patch KVM: nVM: Ensure INVVPID is emulated on the correct physical CPU
Event History
Frequently Asked Questions
Which environments are exposed to this issue?
The issue applies to Linux KVM deployments using nested virtualization, where an L1 guest runs an L2 guest. The described condition involves L1 migrating between physical CPUs while L2's nested VMCS remains associated with the CPU where L2 previously ran.
What sequence triggers the stale TLB condition?
L2 must exit to L1 on one physical CPU, L1 must migrate to another physical CPU and execute INVVPID, and L1 must later resume L2 on the original CPU. In that sequence, INVVPID can run on the migrated CPU while TLB entries associated with L2 remain on the original CPU.
How does the resolved change prevent the problem?
KVM ensures INVVPID is executed on the physical CPU where L2 last ran. If that cannot be done, it clears last_vpid so that the next nested VM-Enter triggers a full VPID flush; KVM also flushes the TLB when L2 runs on a different physical CPU.