[lkml]   [2003]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: problem with blk_queue_bounce_limit()
>>>>> On Fri, 06 Jun 2003 23:44:01 -0700 (PDT), "David S. Miller" <> said:

DaveM> But on an IOMMU system, we could end up mapping to the same
DaveM> bogus DMA address.

Ah, yes, just changing the buffer address doesn't guarantee a
different bus address. I missed that.

DaveM> So we have to solve this problem by keeping the existng bad
DaveM> mapping, doing a new DMA mapping, then trowing away the old
DaveM> one.

But you're creating a new mapping for the old buffer. What if you had
a DMA API implementation which consolidates multiple mapping attempts
of the same buffer into a single mapping entry (along with a reference
count)? That would break the workaround.

Isn't the proper fix to (a) get a new buffer, (b) create a mapping for
the new buffer, (c) destroy the mapping for the old buffer. That
should guarantee a different bus address, no matter what the
DMA-mapping implementation.

Plus then you don't have to rely on PCI_DMA_BUS_IS_PHYS.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:36    [W:0.073 / U:2.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site