Re: Problem Pinning Physical Memory

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Wed, Nov 24, 2010 at 03:55:07PM +0200, Eli Cohen wrote:
> On Mon, Nov 22, 2010 at 06:28:47PM +0000, Brian wrote:
> > ibv_reg_mr works fine as long as the shared region is in RAM. However, if I
> > change the memory region to the physical memory on a PCI device the call to
> > ibv_reg_mr fails. What should I be doing to register a physical memory region?
> > 
> > In searching through this forum I've seen some patches relating to
> > reg_io_mr/dereg_io_mr. However, I don't see those changes in the 1.5.2 ofed
> > sources. I had hoped to try applying the patches myself but the structure of the
> > unchanged code in the patches appears to be different than the 1.5.2 ofed
> > sources. Is there another, more recent, code base that I should be using?
> > 
> 
> You can't regiter IO memory using ibv_reg_mr() - you can only do that
> by registering that memory using physical memory registration which is
> available only for kernel consumers. 

> You can't allow userspace to register physical pages as this is a
> security breach.

Eh? If it is mmap'd into my processes address space then letting it be
used for RDMA makes no difference to the security of the system.

The last time this came up I said that the kernel side of ibv_reg_mr
should do the right thing for all types of memory that are mmap'd into
a process and I still think that is true. RDMA to device memory could
be very useful and with things like GEM managing the allocation of
device (video) memory to userspace, so it can be done safely.

Jason
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