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

[Boris Ostrovsky]

On 02/17/2016 05:18 PM, Andy Lutomirski wrote:
> On Wed, Feb 17, 2016 at 2:03 PM, Borislav Petkov <bp@xxxxxxxxx> 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?
> >
> > > 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...) or something else.
> >
> > What's your preference?
> I'm confused.  Isn't it the other way around?  That is, checking for
> the hypervisor range on all systems should be safer, right?  Or am I
> missing something?

Hmm. I think you are right --- I was following wrong branch of the 'if' 
statement. We are always going straight to note_page().

Then yes, we should be able to remove paravirt_enabled(). Sorry for the 
noise.

-boris