Re: [PATCH 1/3] KVM: nVMX: Always flush vpid02 on first use

[Jim Mattson]

On Tue, Jun 16, 2026 at 2:47 PM Yosry Ahmed <yosry@xxxxxxxxxx> wrote:
>
> Make sure vpid02 is always flushed on first use by setting last_vpid=0
> when allocating vpid02.  nested_vmx_transition_tlb_flush() will always
> detect a VPID change on first VM-Enter after VMXON, because VPID=0 in
> vmcb12 is not allowed if L1 enables VPID.
>
> This avoids using stale TLB entries from a previous lifetime of the
> VPID, that might have been associated with a different vCPU (or a
> completely different VM).
>
> Note that last_vpid is already being initialized as 0 when the vCPU is
> created, but it is not reset when vpid02 is freed on VMXOFF. Hence, the
> problem can only occur if L1 does VMXOFF -> VMXON, runs an L2, and KVM
> happens to reuse a VPID that has TLB entries on the physical CPU.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Yosry Ahmed <yosry@xxxxxxxxxx>
> ---
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>