Subject: Re: Kernel copyin/out optimizations for ARM...
To: None <Richard.Earnshaw@arm.com>
From: Jason R Thorpe <email@example.com>
Date: 03/14/2002 08:14:35
On Thu, Mar 14, 2002 at 11:26:29AM +0000, Richard Earnshaw wrote:
> On reflection, maybe not. IIRC the page tables for the current process
> are mapped linearly at PROCESS_PAGE_TBLS_BASE. So they are there in an
> single array. What happens if a physical page is missing from that map
> and we try to dereference it, I've no idea. I hope we won't end up
> mapping one in, just so that we can decide that it doesn't contain a valid
The pmap is supposed to check that the L1 slot for a VA is valid before
touching the L2 table. If you reference a nonexistent L2 table, you'll
get a fatal data abort (i.e. the VM fault handler won't find a vm_map
mapping for that space and will panic), which is what you want.
-- Jason R. Thorpe <firstname.lastname@example.org>