Xen devel - Jul 2005 - RE: Re: [Xen-changelog] Fix NX/XD enable on secondary CPUs.

Whether the processor is in 32 or 64-bit mode, if NX is used, then
EFER_NX needs to be set. If NX isn''t used, then it''s a
"Don''t care". I
think bad things happens if you set the NX bit in the page table and
don''t have EFER_NX set...

--
Mats 
> -----Original Message-----
> From: xen-devel-bounces@lists.xensource.com 
> [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of 
> Keir Fraser
> Sent: 13 July 2005 11:52
> To: Gerd Knorr
> Cc: xen-devel@lists.xensource.com
> Subject: Re: [Xen-devel] Re: [Xen-changelog] Fix NX/XD enable 
> on secondary CPUs.
> 
> 
> Does EFER_NX need setting for 32-bit PAE?
> 
> We don''t set it for *any* cpus in x86_32 builds, even cpu0...
> 
>   -- Keir
> 
> On 13 Jul 2005, at 11:17, Gerd Knorr wrote:
> 
> > I think I have this problem with PAE as well.  Machine is SMP 
> > (hyperthreaded).  PAE dom0 boots fine on CPU #0.  PAE domU 
> is bound to 
> > CPU #1 by default and boots to the login prompt as well, 
> but only with 
> > NX disabled (and network disabled, but that''s another story
...).
> >
> > With NX-enabled domU boot I get this ...
> >
> >   (XEN) (file=traps.c, line=872) Non-priv domain attempted 
> > RDMSR(c0000080,00000000,20100000).
> >   (XEN) (file=traps.c, line=864) Non-priv domain attempted 
> > WRMSR(c0000080,00000800,00000000).
> >
> > ... and the kernel crashes shortly later, I guess due to NX 
> pte entry 
> > without NX being enabled on CPU #1.  It crashes right after 
> the first 
> > set_fixmap call which creates a pte entry with NX set.
> 
> 
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On 13 Jul 2005, at 11:45, Petersson, Mats wrote:
> Whether the processor is in 32 or 64-bit mode, if NX is used, then
> EFER_NX needs to be set. If NX isn''t used, then it''s a
"Don''t care". I
> think bad things happens if you set the NX bit in the page table and
> don''t have EFER_NX set...
Okay, this should now be fixed in the public repository.

Hopefully domU PAE will boot much further now :-)

  -- Keir


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> Hopefully domU PAE will boot much further now :-)
Yes, works.
Thanks,

  Gerd

-- 
panic("it works"); /* avoid being flooded with debug messages */

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