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Diffstat (limited to 'cover-letter')
| -rw-r--r-- | cover-letter | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/cover-letter b/cover-letter new file mode 100644 index 000000000000..907dd50f08fc --- /dev/null +++ b/cover-letter @@ -0,0 +1,49 @@ +This is just a rebase with minor changes and better comments in the code. + +Previous cover letter (slightly improved): + +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 [1]. + +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 5.1rc1+ but i can rebase it on any specific branch once HMM pre- +requisite is upstream. + +[1] https://cgit.freedesktop.org/~glisse/linux/log/?h=odp-hmm +[2] https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-odp-v2 + +Cc: linux-rdma@vger.kernel.org +Cc: Jason Gunthorpe <jgg@mellanox.com> +Cc: Leon Romanovsky <leonro@mellanox.com> +Cc: Doug Ledford <dledford@redhat.com> +Cc: Artemy Kovalyov <artemyko@mellanox.com> +Cc: Moni Shoua <monis@mellanox.com>, +Cc: Mike Marciniszyn <mike.marciniszyn@intel.com> +Cc: Kaike Wan <kaike.wan@intel.com> +Cc: Dennis Dalessandro <dennis.dalessandro@intel.com> |