Re: [Xen-devel] struct shared_info extensibility (or lack thereof)

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 28 Nov 2005, at 16:47, Rik van Riel wrote:

> The reason for putting the vcpu_* structures together on a per
> virtual cpu basis is that this way we can extend the number of
> virtual CPUs in the future, without breaking the interface with
> older guests.
>
> The current stared_info struct of two [MAX_VIRT_CPUS] arrays
> followed by the single variables is just impossible to extend
> in the future.
MAX_VIRT_CPUS is already quite big (32). Increasing it to the next 
power-of-two will overflow the shared_info page. So, if/when we want to 
do that we'll place the extra vcpu info in a separate shared page.
Given how close 3.0.0 is now, I don't think this is a good change to be 
making.
 -- Keir


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