Re: [PATCH] KVM: nVMX: nested VPID emulation

[Wanpeng Li]

On 9/16/15 1:32 AM, Jan Kiszka wrote:
> On 2015-09-15 12:14, Wanpeng Li wrote:
> > On 9/14/15 10:54 PM, Jan Kiszka wrote:
> > > Last but not least: the guest can now easily exhaust the host's pool of
> > > vpid by simply spawning plenty of VCPUs for L2, no? Is this acceptable
> > > or should there be some limit?
> > I reuse the value of vpid02 while vpid12 changed w/ one invvpid in v2,
> > and the scenario which you pointed out can be avoid.
> I cannot yet follow why there is no chance for L1 to consume all vpids
> that the host manages in that single, global bitmap by simply spawning a
> lot of nested VCPUs for some L2. What is enforcing L1 to call nested
> vmclear - apparently the only way, besides destructing nested VCPUs, to
> release such vpids again?

In v2, there is no direct mapping between vpid02 and vpid12, the vpid02 
is per-vCPU for L0 and reused while the value of vpid12 is changed w/ 
one invvpid during nested vmentry. The vpid12 is allocated by L1 for L2, 
so it will not influence global bitmap(for vpid01 and vpid02 allocation) 
even if spawn a lot of nested vCPUs.

Regards,
Wanpeng Li

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/