HEADS UP Re: cvs commit: src/sys/conf options.i386 src/sys/i386/i386 bios.c locore.s machdep.c mpboot.s pmap.c vm86bios.s vm_machdep.c src/sys/i386/include _types.h bus_at386.h param.h pmap.

Mike Silbersack silby at silby.com
Mon Mar 31 00:53:03 PST 2003

On Mon, 31 Mar 2003, Jake Burkholder wrote:

> PAE makes the page table entries bigger so they can hold 64 bit physical
> addresses, but it does not give you more of them, pointers are still 32bit.
> On x86 the kernel is mapped into each process' address space, which is why
> it takes a chunk of it, and this is how copyin and copyout work, you can
> just access the current process' address space directly.  All copyin and
> copyout do on x86 is handle page faults due to unmapped user memory, which
> should not normally happen in kernel mode.  If they were separate this would
> be much more complicated, and entering the kernel would require switching
> address space, instead of just increasing the priviledge level.
> Jake

Doh, that makes perfect sense, I didn't think it through before asking.

Changing it around to have seperate address spaces sounds like more work
than PAE, now that I think more about it.  I'll just wait for true 64 bit
machines before asking for a large KVA. :)

Thanks for the explanation,

Mike "Silby" Silbersack

More information about the cvs-src mailing list