Re: kmem_alloc replacement in Tiger
Re: kmem_alloc replacement in Tiger
- Subject: Re: kmem_alloc replacement in Tiger
- From: Terry Lambert <email@hidden>
- Date: Wed, 1 Feb 2006 17:12:07 -0800
On Feb 1, 2006, at 3:58 PM, Andrew Gallatin wrote:
Terry Lambert writes:
[...]
You've confused me. What 32-bit value? I wasn't asking about how
to handle a 64-bit user virtual address. We already do this.
It sounded like you were trying to use a 32 bit physical address...
My concern was with avoiding bouncing a 64-bit physical address which
backs a 32-bit kernel virtual address (or a 32- or 64-bit user virtual
address).
This should not be a problem, and should not require bouncing, unless
there's a hardware limitation. The kernel itself only really deals
with virtual addresses. Physical addresses are handled by the pmap
layer. In practice, it's impossible to have a machine where you are
using memory that has a pmap entry referring to it that can't refer to
it because it didn't have enough bits to establish the mapping in the
first place. The attempt to map it would have failed.
-- Terry
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