Thanks for your reply!
I am trying to write a gen2 based kernel module here. Basically, what
I am trying to do is to send a one byte kernel buffer to a remote user
process. I used get_dma_mr to get the mr before hand at the sender side,
so that I don't have to bother to register when sending the kernel
buffer. Since I am working on IA-32 machine, so I assume bus addr and
phys addr are the same(I tried both virt_to_phys and dma_map_single()
for addresss translation actually).
What I noticed was that if the buffer is above in high memory, the
data was not received correctly; while if in low memory, things work.
Does this mean HCA is not able to address high memory or maybe I am
missing sth here?
Thanks
Shuang,
Caitlin Bestler wrote:
[EMAIL PROTECTED] wrote:
On Thu, Nov 17, 2005 at 12:33:22AM -0500, Shuang Liang wrote:
Hi,
I am new here with some problem of gen2 programming, hope somebody
can help me. I was trying to send a message from a kernel buffer to a
remote userland program on IA-32 machines.
Basically, what happened was I used get_dma_mr to get memory
registered. And I noticed if a buffer is allocated from high memory
(address >f8000000), then the data can not be delivered correctly to
the receiver side(both send recv completes successfully, but with
wrong data). I thought the problem could have been that I used
virt_to_phys for address translation.
Using "virt_to_phys" is always wrong when trying to get a DMA mapping.
But I can't find any appropriate ones for high memory address
translation. I wondering if somebody could give me some suggestions
on this.
I don't know enough context.
Are you trying to write an openib kernel driver?
If so you want to read "Documentation/DMA-API.txt" for hints
on the available DMA mapping interfaces and then look at how
SDP or IPoIB use the described DMA interfaces.
That applies even if you are trying to write a kernel daemon
and wish to use high memory. You either make it part of your
virtual memory map at least temporarily, so you can register
it, or you register the memory "physically". But "physical"
registration for RDMA is never really physical addresses, it
is always bus addresses, which means reading the stuff meant
for driver developers.
--
Shuang Liang,
Graduate Administration Assistant,
Department of Computer Science & Engineering
The Ohio State University, 374 Dreese Labs, 2015 Neil Ave
Columbus, Ohio 43210
614-292-1900,
614-292-2911 (fax)
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