Re: [discuss] [patch] x86_64: align and pad x86_64 GDT on page boundary

[Andi Kleen <ak@suse.de>]

On Thu, Dec 08, 2005 at 03:09:17PM -0800, Rohit Seth wrote:
> On Thu, 2005-12-08 at 13:55 -0800, Ravikiran G Thirumalai wrote:
> > On Thu, Dec 08, 2005 at 09:15:18PM +0100, Andi Kleen wrote:
> > > On Thu, Dec 08, 2005 at 11:42:32AM -0800, Ravikiran G Thirumalai
> > wrote:
> > > > 
> > > > -   .align  L1_CACHE_BYTES
> > > > +   /* zero the remaining page */
> > > > +   .fill PAGE_SIZE / 8 - GDT_ENTRIES,8,0
> > > > +  
> > > >  ENTRY(idt_table)  
> > >
> > > Why can't the IDT not be shared with the GDT page? It should be
> > mostly
> > > read only right and putting r-o data on that page should be ok,
> > right?
> > 
> > Yes, you are right.  This should not have been a problem. 
> > Some people reported this symbol (cpu_gdt) though.  Will have to go
> > back and
> > check.
> 
> IIRC, Zach's patches for gdt alignment, moved the gdts from per_cpu data
> structure to each secondary CPU dynamically allocating page for its gdt.

Kiran's patch does this too.  Except for the BP GDT, which could
be shared with the single IDT.

-Andi (who actually plans to attack per CPU IDTs at some point
so this could change later)