RE: [PATCH v2 4/4] nested vmx: use a list to store the launched vmcs12 for L1 VMM

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> -----Original Message-----
> From: Gleb Natapov [mailto:gleb@xxxxxxxxxx]
> Sent: Wednesday, November 28, 2012 7:28 PM
> To: Marcelo Tosatti
> Cc: Xu, Dongxiao; kvm@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 4/4] nested vmx: use a list to store the launched vmcs12
> for L1 VMM
> 
> On Tue, Nov 27, 2012 at 10:29:08PM -0200, Marcelo Tosatti wrote:
> > On Thu, Nov 22, 2012 at 12:51:59PM +0800, Dongxiao Xu wrote:
> > > The launch state is not a member in the VMCS area, use a separate
> > > variable (list) to store it instead.
> > >
> > > Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> >
> > 1. What is the problem with keeping launched state in the VMCS?
> > Assuming there is a positive answer to the above:
> >
> > 2. Don't you have to change VMCS ID?
> >
> > 3. Can't it be kept somewhere else other than a list? Current scheme
> > allows guest to allocate unlimited amounts of host memory.
> >
> > 4. What is the state of migration / nested vmx again? If vmcs12 is
> > migrated, this means launched state is not migrated anymore.
> >
> > Patches 1-3 seem fine.
> According to Dongxiao they are slowing down nested guest by 4%.

For this version, it will introduce certain performance downgrade. 

Actually in my new patch, I simplified the vmcs12_read() and vmcs12_write() functions and there is no obvious performance downgrade.

Thanks,
Dongxiao

> 
> --
> 			Gleb.
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