linux-kernel - Re: [PATCH] KVM: nVMX: nested VPID emulation

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Message-ID: <55F8563D.3050905@siemens.com>
Date:	Tue, 15 Sep 2015 19:32:45 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Wanpeng Li <wanpeng.li@...mail.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: nVMX: nested VPID emulation

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?

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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