Re: [PATCH v2 3/3] paravirt: rename paravirt_enabled to paravirt_legacy

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 02/17/2016 05:03 PM, Borislav Petkov wrote:
> On Wed, Feb 17, 2016 at 04:21:56PM -0500, Boris Ostrovsky wrote:
>> That's exactly the point: if something is mapped it's an error for a
>> non-PV kernel.
> How would something be mapped there? __PAGE_OFFSET is
> 0xffff880000000000.
>
> Or are you thinking about some insanely b0rked kernel code mapping stuff
> in there?

The latter. This is to detect things that clearly shouldn't be happening.

>
>> By removing paravirt_enabled() we may miss those errors. Worse, I think we
>> may even crash while doing pagetable walk (although it's probably better to
>> crash here than to use an unexpected translation in real code somewhere)
> Well, if this is the only site which keeps paravirt_enabled() from being
> buried, we need to think about a better way to detect a hypervisor.
> Maybe we should look at x86_hyper, use CPUID(0x4...)

Can't use CPUID 0x40000000 because it will return hypervisor (Xen or 
otherwise) for non-PV guests as well. In Xen's case, you can't determine 
guest type from hypervisor leaves.


> or something else.

We could say xen_pv_domain(). But this means using Xen-specific code in 
x86-generic file to detect things specified by ABI. I don't know if I'd 
like that.

-boris

>
> What's your preference?
>