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On Thu, May 02, 2002 at 03:20:39PM -0700, Martin J. Bligh wrote: > > On Thu, May 02, 2002 at 08:41:36PM +0200, Andrea Arcangeli wrote: > >> but can you plugin 32bit pci hardware into your 64bit-pci slots, right? > >> If not, and if you're also sure the linux drivers for your hardware are all > >> 64bit-pci capable then you can do the changes regardless of the 4G > >> limit, in such case you can spread the direct mapping all over the whole > >> 64G physical ram, whereever you want, no 4G constraint anymore. > > > > I believe 64-bit PCI is pretty much taken to be a requirement; if it > > weren't the 4GB limit would once again apply and we'd be in much > > trouble, or we'd have to implement a different method of accommodating > > limited device addressing capabilities and would be in trouble again. > > IIRC, there are some funny games you can play with 32bit PCI DMA. > You're not necessarily restricted to the bottom 4Gb of phys addr space, > you're restricted to a 4Gb window, which you can shift by programming > a register on the card. Fixing that register to point to a window for the > node in question allows you to allocate from a node's pg_data_t and > assure DMAable RAM is returned. if you've as many windows as the number of nodes than you're just fine in all cases. you only need to teach pci_map_single and friends to return the right bus address that won't be an identity anymore with the phys addr, then you can forget the >4G phys constraint on the pages returned by zone_normal :). Andrea - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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