Re: [Milkymist port] virtual memory management

[Matt Thomas <matt%3am-software.com@localhost>]

On Feb 18, 2014, at 3:54 AM, Yann Sionneau <yann.sionneau%gmail.com@localhost> 
wrote:

> Le 10/02/14 23:00, Yann Sionneau a écrit :
>> Thanks for all your explanations, if everything I said here is correct 
>> (which would mean I understood correctly your answer) then I think I'm ready 
>> to implement all this :)
> 
> Hi,
> 
> I have made good progress on the NetBSD port, it is now booting up to 
> enabling interrupts and cpu_initclocks() call, see the boot log [0].
> 
> But then I am wondering how I can map the memory mapped registers of the 
> timer0 of Milkymist SoC in order to use it as the main ticking clock.
> 
> Basically, I need to map physical address 0xe000.1000 somewhere in kernel 
> virtual memory.
> 
> Is there somewhere a function like vaddr_t map_paddr(paddr_t, prot)?
> 
> I could indeed walk the kernel page table and insert somewhere in a free PTE 
> (a NULL one) a reference to the 0xe000.1000 physical address, but then how to 
> be sure that the vm subsystem will not allocate this virtual address twice?
> 
> Is there an "iomapping" mechanism?
> 
> Thank you for your help :)
> 
> [0] -- http://pastebin.com/MYitt9L4

see bus_space(9), specifically bus_space_map.

internally, it allocates some KVA via uvm and uses pmap_kenter_pa to 
map the I/O address via the allocated KVA.