Re: 40 vs 44 bit memory addressing HP DL580/980

From: John Baldwin <jhb_at_freebsd.org>
Date: Mon, 22 Nov 2010 14:47:12 -0500
On Monday, November 22, 2010 1:37:45 pm Alan Cox wrote:
> On Mon, Nov 22, 2010 at 6:59 AM, John Baldwin <jhb_at_freebsd.org> wrote:
> 
> > On Sunday, November 21, 2010 8:05:26 pm Sean Bruno wrote:
> > > Looks like these HP boxes have the capability to do 44 bit memory
> > > addressing if configured to do so from the BIOS.
> > >
> > > Is anyone interested in any data from that setting?
> >
> > Does it boot ok? :)  The MTRR code should handle that (there is a CPUID
> > field that tells the OS how many bits are significant).  Not sure if there
> > are any places in the pmap that assume 40 bits, but a test boot is
> > certainly
> > worth trying.
> >
> >
> Since we don't boot with 40-bit addressing, I can easily predict the
> outcome.  :-)
> 
> The trouble with this machine is that the second 128GB of RAM is being
> placed between 512G and 1T in the physical address space, which is beyond
> the range of the (current) direct map.  So, we take a page fault on the
> first access to a page in the second 128GB through the direct map.

Heh, I guess that is what your earlier patch did?  Once that patch is applied
I think Sean should just try 44-bit mode if so.

-- 
John Baldwin
Received on Mon Nov 22 2010 - 18:49:24 UTC

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