Re: [Xen-devel] [PATCH 4/4] xen/PVH: Remove reserved entry in PVH GDT

[Boris Ostrovsky]

On 05/01/2018 04:00 AM, Roger Pau Monnà wrote:
> On Mon, Apr 30, 2018 at 12:23:39PM -0400, Boris Ostrovsky wrote:
> > And without it we can't use _BOOT_XX macros any longer so define new ones.
>
> Not being that familiar with Linux internals I'm not sure I see the
> benefit of this. Isn't there a risk that some other code is going to
> use the __BOOT_XX defines?

The startup code we are jumping to loads their own GDT and I don't see 
any explicit references to segments.

The reason I added this patch was that since we are adding another 
segment descriptor (GS) we are now using PVH-specific GDT and so we are 
not sharing layout with other code anymore. (Also, the new GS segment 
overlaps with __BOOT_TSS so I kind of broke it already there, not 
unintentionally).

But if people think I should stick with __BOOT_XX I can drop this patch 
(and then probably move GS down one entry).


-boris