Re: [PATCH 4/5] KVM: MMU: store generation-number into mmio spte

Gleb Natapov
2013-03-18T12:49:04Z

On Mon, Mar 18, 2013 at 08:42:09PM +0800, Xiao Guangrong wrote:
> On 03/18/2013 07:19 PM, Paolo Bonzini wrote:
> > Il 15/03/2013 16:29, Xiao Guangrong ha scritto:
> >> +/*
> >> + * spte bits of bit 3 ~ bit 11 are used as low 9 bits of
> >> + * generation, the bits of bits 52 ~ bit 61 are used as
> >> + * high 12 bits of generation.
> >> + */
> >
> > High 10 bits.
>
> Yes, i forgot to update the comments! Thank you, Paolo!
>
> >
> > How often does the generation number change? Especially with Takuya's
> > patches, using just 10 bits for the generation might be enough and
> > simplifies the code.
>
> I guess it's only updated when guest is initializing and doing hotplug.
> In my origin thought, if the number is big enough that it could not
> round on all most case of hotplug, the things introduced by Takuya is
> not necessary. But, if you guys want to keep the things, 10 bits should
> be enough. :)
I think you encapsulated the 19bit generation number handling good enough, so
I personally do not mind making it as big as we can.

--
Gleb.