Re: [Xen-devel] [edk2-devel] [PATCH v4 20/35] OvmfPkg/XenPlatformPei: Introduce XenPvhDetected

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Wed, Aug 07, 2019 at 05:03:46PM +0200, Roger Pau Monné wrote:
> On Mon, Jul 29, 2019 at 04:39:29PM +0100, Anthony PERARD wrote:
> > +BOOLEAN
> > +XenPvhDetected (
> > +  VOID
> > +  )
> > +{
> > +  //
> > +  // This function should only be used after XenConnect
> > +  //
> > +  ASSERT (mXenInfo.VersionMajor != 0);
> 
> That's IMO dangerous. Using the version as an indication that
> XenConnect has run seems like a bad idea, since returning a major
> version of 0 is a valid number to return. Can't you check against
> something else that doesn't depends on hypervisor provided data? (ie:
> like some allocations or such that happen in XenConnect)
> 
> A paranoid could provider could even return major == 0 and minor == 0
> in order to attempt to hide the Xen version used, since guests are not
> supposed to infer anything from the Xen version, available hypervisor
> features are reported by other means.

I'm sure a paranoid provider wouldn't use a debug build of OVMF :-). So
that assert doesn't matter. There's nothing dangerous in a `nop'! :-D

But I could use mXenInfo.HyperPages instead.

Thanks,

-- 
Anthony PERARD

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