* Re: [PATCH] ppc64: 64K pages support
[not found] ` <1130916198.20136.17.camel@gaston>
@ 2005-11-05 0:38 ` Christoph Hellwig
2005-11-05 0:44 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 3+ messages in thread
From: Christoph Hellwig @ 2005-11-05 0:38 UTC (permalink / raw)
To: Benjamin Herrenschmidt
Cc: Andrew Morton, linuxppc64-dev, Linus Torvalds, Linux Kernel list,
linux-mm
So how does the 64k on 4k hardware emulation work? When Hugh did
bigger softpagesize for x86 based on 2.4.x he had to fix drivers all
over to deal with that.
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* Re: [PATCH] ppc64: 64K pages support
2005-11-05 0:38 ` [PATCH] ppc64: 64K pages support Christoph Hellwig
@ 2005-11-05 0:44 ` Benjamin Herrenschmidt
2005-11-05 6:37 ` Dave Airlie
0 siblings, 1 reply; 3+ messages in thread
From: Benjamin Herrenschmidt @ 2005-11-05 0:44 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Andrew Morton, linuxppc64-dev, Linus Torvalds, Linux Kernel list,
linux-mm
On Sat, 2005-11-05 at 01:38 +0100, Christoph Hellwig wrote:
> So how does the 64k on 4k hardware emulation work? When Hugh did
> bigger softpagesize for x86 based on 2.4.x he had to fix drivers all
> over to deal with that.
What was the problem with drivers ? On ppc64, it's all hidden in the
arch code. All the kernel sees is a 64k page size. I extended the PTE to
contain tracking informations for the 16 sub pages (HPTE bits & hash
slot index). Sub pages are faulted on demand and flushed all at once,
but it's all transparent to the generic code.
Ben.
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* Re: [PATCH] ppc64: 64K pages support
2005-11-05 0:44 ` Benjamin Herrenschmidt
@ 2005-11-05 6:37 ` Dave Airlie
0 siblings, 0 replies; 3+ messages in thread
From: Dave Airlie @ 2005-11-05 6:37 UTC (permalink / raw)
To: Benjamin Herrenschmidt
Cc: Christoph Hellwig, Andrew Morton, linuxppc64-dev, Linus Torvalds,
Linux Kernel list, linux-mm
> What was the problem with drivers ? On ppc64, it's all hidden in the
> arch code. All the kernel sees is a 64k page size. I extended the PTE to
> contain tracking informations for the 16 sub pages (HPTE bits & hash
> slot index). Sub pages are faulted on demand and flushed all at once,
> but it's all transparent to the generic code.
>
We did that with the VAX port about 5 years ago :-), granted for
different reasons..
The VAX has 512 byte hw pages, we had to make a 4K pagesize for the
kernel by grouping 8 hw pages together and hiding it all in the arch
dir..
granted I don't know if it broke any drivers, we didn't have any...
Dave.
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^ permalink raw reply [flat|nested] 3+ messages in thread
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[not found] ` <1130916198.20136.17.camel@gaston>
2005-11-05 0:38 ` [PATCH] ppc64: 64K pages support Christoph Hellwig
2005-11-05 0:44 ` Benjamin Herrenschmidt
2005-11-05 6:37 ` Dave Airlie
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