Re: [Xen-users] a few questions about superpage support

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-09-12 at 16:16 -0700, Antonin Bas wrote:
> - libxc default policy is to NOT activate that flag unless it is
> explicitly specified by the user: the extended feature bits are
> handled by the vendor specific functions in tools/libxc/xc_cpuid_x86.c

Ah, I'd forgotten there was policy in libxc as well.

> -in our case intel_xc_cpuid_policy(). Examination of this function
> reveals that the default behavior is to keep the pdpe1gb bit off
> (other flags, like rdtscp are set to on by default for x86_64
> architectures).

I suppose the thinking was not to let guests hoover up contiguous 1GB
regions by default.

> I managed to enable it by adding cpuid="host,page1gb=k" to my guest
> configuration file.
> 
> Please tell me if anything I said does not make sense. Thanks.

It makes perfect sense.

Ian.


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