linux-kernel - Re: [PATCH v3 0/1] Use HMM for ODP v3

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Date:   Thu, 11 Apr 2019 12:29:43 +0000
From:   Leon Romanovsky <leonro@...lanox.com>
To:     "jglisse@...hat.com" <jglisse@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Doug Ledford <dledford@...hat.com>,
        Artemy Kovalyov <artemyko@...lanox.com>,
        Moni Shoua <monis@...lanox.com>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Kaike Wan <kaike.wan@...el.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>
Subject: Re: [PATCH v3 0/1] Use HMM for ODP v3

On Wed, Apr 10, 2019 at 11:41:24AM -0400, jglisse@...hat.com wrote:
> From: Jérôme Glisse <jglisse@...hat.com>
>
> Changes since v1/v2 are about rebase and better comments in the code.
> Previous cover letter slightly updated.
>
>
> This patchset convert RDMA ODP to use HMM underneath this is motivated
> by stronger code sharing for same feature (share virtual memory SVM or
> Share Virtual Address SVA) and also stronger integration with mm code to
> achieve that. It depends on HMM patchset posted for inclusion in 5.2 [2]
> and [3].
>
> It has been tested with pingpong test with -o and others flags to test
> different size/features associated with ODP.
>
> Moreover they are some features of HMM in the works like peer to peer
> support, fast CPU page table snapshot, fast IOMMU mapping update ...
> It will be easier for RDMA devices with ODP to leverage those if they
> use HMM underneath.
>
> Quick summary of what HMM is:
>     HMM is a toolbox for device driver to implement software support for
>     Share Virtual Memory (SVM). Not only it provides helpers to mirror a
>     process address space on a device (hmm_mirror). It also provides
>     helper to allow to use device memory to back regular valid virtual
>     address of a process (any valid mmap that is not an mmap of a device
>     or a DAX mapping). They are two kinds of device memory. Private memory
>     that is not accessible to CPU because it does not have all the expected
>     properties (this is for all PCIE devices) or public memory which can
>     also be access by CPU without restriction (with OpenCAPI or CCIX or
>     similar cache-coherent and atomic inter-connect).
>
>     Device driver can use each of HMM tools separatly. You do not have to
>     use all the tools it provides.
>
> For RDMA device i do not expect a need to use the device memory support
> of HMM. This device memory support is geared toward accelerator like GPU.
>
>
> You can find a branch [1] with all the prerequisite in. This patch is on
> top of rdma-next with the HMM patchset [2] and mmu notifier patchset [3]
> applied on top of it.
>
> [1] https://cgit.freedesktop.org/~glisse/linux/log/?h=rdma-5.2

Hi Jerome,

I took this branch and merged with our latest rdma-next, but it doesn't
compile.

In file included from drivers/infiniband/hw/mlx5/mem.c:35:
./include/rdma/ib_umem_odp.h:110:20: error: field _mirror_ has
incomplete type
  struct hmm_mirror mirror;
                      ^~~~~~
./include/rdma/ib_umem_odp.h:132:18: warning: _struct hmm_range_ declared inside parameter list will not be visible outside of this definition or declaration
struct hmm_range *range);
	^~~~~~~~~
make[4]: *** [scripts/Makefile.build:276: drivers/infiniband/hw/mlx5/mem.o] Error 1

The reason to it that in my .config, ZONE_DEVICE, MEMORY_HOTPLUG and HMM options were disabled.

Thanks

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