* 64GB (i386) kernel config + PAGE_OFFSET change
@ 2002-02-22 18:09 Badari Pulavarty
2002-02-22 19:20 ` Hugh Dickins
0 siblings, 1 reply; 3+ messages in thread
From: Badari Pulavarty @ 2002-02-22 18:09 UTC (permalink / raw)
To: linux-kernel; +Cc: andrea
Hi,
I am trying to boot a 2.4.17 (i386) kernel with 64GB kernel config
and PAGE_OFFSET changed to 3.5 GB (0xE0000000) and it does not boot.
I was wondering why ? I have 8GB on my machine (P-III). I looked
at Andrea's 3.5 GB user-virtual patch. It does not support 3.5GB
for 64GB kernel either ? I can't boot even with forcing mem=1G either.
Is there something fundamental here ?
Please let me know.
Thanks,
Badari
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: 64GB (i386) kernel config + PAGE_OFFSET change
2002-02-22 18:09 64GB (i386) kernel config + PAGE_OFFSET change Badari Pulavarty
@ 2002-02-22 19:20 ` Hugh Dickins
2002-02-22 19:39 ` Andrea Arcangeli
0 siblings, 1 reply; 3+ messages in thread
From: Hugh Dickins @ 2002-02-22 19:20 UTC (permalink / raw)
To: Badari Pulavarty; +Cc: linux-kernel, andrea
On Fri, 22 Feb 2002, Badari Pulavarty wrote:
>
> I am trying to boot a 2.4.17 (i386) kernel with 64GB kernel config
> and PAGE_OFFSET changed to 3.5 GB (0xE0000000) and it does not boot.
>
> I was wondering why ? I have 8GB on my machine (P-III). I looked
> at Andrea's 3.5 GB user-virtual patch. It does not support 3.5GB
> for 64GB kernel either ? I can't boot even with forcing mem=1G either.
With NOHIGHMEM or HIGHMEM4G, there are 2 levels of page table:
1024 entries in pgd, (1 entry per pmd,) 1024 entries per pt.
With HIGHMEM64G (PAE: 8-byte pte), there are 3 levels of page table:
4 entries in pgd, 512 entries per pmd, 512 entries per pt.
The current code only works if PAGE_OFFSET is a multiple of PGDIR_SIZE:
any multiple of 0x00400000 if NOHIGHMEM or HIGHMEM4G, but the more
limiting multiple of 0x40000000 if HIGHMEM64G: so 3.5 GB not allowed.
I expect the CONFIG_X86_PAE get_pgd_slow() could quite easily be
extended to copy kernel entries at pmd level as well as at pgd level
if necessary, but so far nobody has wanted it enough to make the change.
Hugh
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: 64GB (i386) kernel config + PAGE_OFFSET change
2002-02-22 19:20 ` Hugh Dickins
@ 2002-02-22 19:39 ` Andrea Arcangeli
0 siblings, 0 replies; 3+ messages in thread
From: Andrea Arcangeli @ 2002-02-22 19:39 UTC (permalink / raw)
To: Hugh Dickins; +Cc: Badari Pulavarty, linux-kernel
On Fri, Feb 22, 2002 at 07:20:57PM +0000, Hugh Dickins wrote:
> if necessary, but so far nobody has wanted it enough to make the change.
exactly, and if somebody wants to make that change only make sure to
left it inside some #ifdef, so we don't slowdown the 3G standard option.
Andrea
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2002-02-22 19:39 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2002-02-22 18:09 64GB (i386) kernel config + PAGE_OFFSET change Badari Pulavarty
2002-02-22 19:20 ` Hugh Dickins
2002-02-22 19:39 ` Andrea Arcangeli
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