mapping small parts of a pci card to conserve KVA
Warner Losh
imp at bsdimp.com
Tue Feb 15 12:54:44 PST 2005
> I maintain drivers for a PCI card which presents itself as having
> 16MB of address space. Eg:
>
> mx0: <Myrinet PCIXE> mem 0xf9000000-0xf9ffffff irq 20 at device 3.0 on pci1
>
> However, most of that address space does not need to be mapped into
> the host. Really, only a little over 2MB needs to be mapped (3 regions
> with length 1024 bytes, 256 bytes, and 2MB).
>
> I've tried to re-write things so that I make multiple calls
> to bus_alloc_resource() with the (hopefully) appropriate offset and
> lengths. Eg:
>
> rid = PCIR_MAPS;
> *res = bus_alloc_resource(is->arch.dev, SYS_RES_MEMORY, &rid,
> (u_long)offset,
> (u_long)(offset + len - 1), len,
> RF_ACTIVE|PCI_RF_DENSE);
>
> At least on 5.3R, I seem to get back the same struct resource * from
> each call. rman_get_virtual() returns a different kva for each
> mapping, yet they all seem to map to the same physical address.
> Eg, I call vtophys() on the results of rman_get_virtual(),
> for each segment, and they all map to 0xf9000000.
>
> Is there a way to just map what I need?
There's no way to map part of a resource currently. I'd like to
create an API to do that, since it would be useful for a lot of
things, but none exists today. As soon as bus_activate_resource is
called, it gets mapped.
Warner
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