[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-rdma
Subject:    Re: IB_MR_TYPE_SG_GAPS support
From:       Christoph Hellwig <hch () infradead ! org>
Date:       2021-08-30 8:29:51
Message-ID: YSyW/3T4w6LfrDdZ () infradead ! org
[Download RAW message or body]

On Sun, Aug 29, 2021 at 04:46:52PM +0300, Max Gurtovoy wrote:
> > > I have a report that net/sunrpc/xprtrdma/frwr_ops.c::frwr_map()
> > > is attempting to register a mix of GPU and CPU pages with a
> > > single MR during an NFSv4 READ.
> > What GPU pages?
> 
> I guess it's GPU device memory.
> 
> But as Jason mentioned, This is still not supported in RDMA. So there should
> be a bounce buffer in the IO path between GPU and CPU memory subsystems.

Well, the RDMA stack does support P2P pages, which can be exported by
GPUs.  It also supports device private pages by migrating them back to
the CPU through hmm_range_fault.  But none of this should require
SG_GAPS.
[prev in list] [next in list] [prev in thread] [next in thread]