From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Tucker Subject: Re: [Suspected SPAM] Re: [RFC PATCH 2/4] uverbs: Add common ib_iomem_get service Date: Thu, 29 Jul 2010 21:16:26 -0500 Message-ID: <4C5235FA.2080001@opengridcomputing.com> References: <20100729162339.14674.15788.stgit@build.ogc.int> <20100729162509.14674.34237.stgit@build.ogc.int> <1280427723.6820.56.camel@chromite.mv.qlogic.com> <4C51D15F.8060708@opengridcomputing.com> <20100729201317.GA7920@obsidianresearch.com> <20100729204150.GC7920@obsidianresearch.com> <1280443789.6820.153.camel@chromite.mv.qlogic.com> <20100729225705.GC26390@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100729225705.GC26390-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Ralph Campbell , "rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "brandt-4OHPYypu0djtX7QSmKvirg@public.gmane.org" , "swise-/Yg/VP3ZvrM@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On 7/29/10 5:57 PM, Jason Gunthorpe wrote: >> You would need to modify ib_umem_get() to check for the VM_PFNMAP >> flag and build the struct ib_umem similar to the proposed >> ib_iomem_get(). However, the page reference counting/sharing issue >> would need to be solved. I think there are kernel level callbacks >> for this that could be used. >> > But in this case the pages are already mmaped into a user process, > there must be some mechanism to ensure they don't get pulled away?! > > This is not virtual memory. It's real memory. > Though, I guess, what happens if you hot un-plug the PCI-E card that > has a process mmaping its memory?! > > Exactly. The memory would have to be physically detached for it to get 'pulled away' > What happens if you RDMA READ from PCI-E address space that does not > have any device responding? > > bus error. > Jason > -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html