Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?]

From: William Lee Irwin III (
Date: Thu May 02 2002 - 16:28:10 EST

On Thu, May 02, 2002 at 08:41:36PM +0200, Andrea Arcangeli wrote:
>> 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.

On Thu, May 02, 2002 at 03:20:39PM -0700, Martin J. Bligh wrote:
> 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.
> M.

Woops, I forgot about the BAR, thanks. Heck, IIRC you were even the one
who told me about this trick.

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