Re: [Xen-devel] Maximum number of vcpus for HVM?

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/11/16 09:36, Juergen Gross wrote:
> According to
>
> https://wiki.xenproject.org/wiki/Xen_Project_Release_Features
>
> HVM guests can have up to 256 vcpus. The definition in
>
> include/public/hvm/hvm_info_table.h:
>
> /* Maximum we can support with current vLAPIC ID mapping. */
> #define HVM_MAX_VCPUS        128
>
> and its usage in domain_max_vcpus(d) suggests the limit is 128.
> I guess we should update the wiki page?

The wiki has been wrong for several releases now, and I have tried
multiple times to get it corrected.

Unfortunately, I don't know what the policy is on retrofitting
corrections to official documentation like that.

Also, it should read "maximum configurable vcpus", not supported.  There
is currently no formally-written support statement, and 64vcpu HVM
guests can definitely cause 5-second watchdog timeouts in Xen under some
circumstances.  This is why XenServer support statement is 32 vcpus.

~Andrew

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