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2021-10-28RDMA/umem: Allow pinned dmabuf umem usageGal Pressman1-0/+11
Introduce ib_umem_dmabuf_get_pinned() which allows the driver to get a dmabuf umem which is pinned and does not require move_notify callback implementation. The returned umem is pinned and DMA mapped like standard cpu umems, and is released through ib_umem_release() (incl. unpinning and unmapping). Link: https://lore.kernel.org/r/20211012120903.96933-3-galpress@amazon.com Signed-off-by: Gal Pressman <galpress@amazon.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2021-08-24RDMA: Use the sg_table directly and remove the opencoded version from umemMaor Gottlieb1-7/+5
This allows using the normal sg_table APIs and makes all the code cleaner. Remove sgt, nents and nmapd from ib_umem. Link: https://lore.kernel.org/r/20210824142531.3877007-4-maorg@nvidia.com Signed-off-by: Maor Gottlieb <maorg@nvidia.com> Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2021-08-24lib/scatterlist: Fix wrong update of orig_nentsMaor Gottlieb1-0/+1
orig_nents should represent the number of entries with pages, but __sg_alloc_table_from_pages sets orig_nents as the number of total entries in the table. This is wrong when the API is used for dynamic allocation where not all the table entries are mapped with pages. It wasn't observed until now, since RDMA umem who uses this API in the dynamic form doesn't use orig_nents implicit or explicit by the scatterlist APIs. Fix it by changing the append API to track the SG append table state and have an API to free the append table according to the total number of entries in the table. Now all APIs set orig_nents as number of enries with pages. Fixes: 07da1223ec93 ("lib/scatterlist: Add support in dynamic allocation of SG table from pages") Link: https://lore.kernel.org/r/20210824142531.3877007-3-maorg@nvidia.com Signed-off-by: Maor Gottlieb <maorg@nvidia.com> Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2021-01-20RDMA/umem: Support importing dma-buf as user memory regionJianxin Xiong1-3/+45
Dma-buf is a standard cross-driver buffer sharing mechanism that can be used to support peer-to-peer access from RDMA devices. Device memory exported via dma-buf is associated with a file descriptor. This is passed to the user space as a property associated with the buffer allocation. When the buffer is registered as a memory region, the file descriptor is passed to the RDMA driver along with other parameters. Implement the common code for importing dma-buf object and mapping dma-buf pages. Link: https://lore.kernel.org/r/1608067636-98073-2-git-send-email-jianxin.xiong@intel.com Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com> Reviewed-by: Sean Hefty <sean.hefty@intel.com> Acked-by: Michael J. Ruhl <michael.j.ruhl@intel.com> Acked-by: Christian Koenig <christian.koenig@amd.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-11-16RDMA/mlx5: Use ib_umem_find_best_pgoff() for SRQJason Gunthorpe1-0/+42
SRQ uses a quantized and scaled page_offset, which is another variation of ib_umem_find_best_pgsz(). Add mlx5_umem_find_best_quantized_pgoff() to perform this calculation for each mailbox. A macro shows how the calculation is directly connected to the mailbox format. This new routine replaces the limited mlx5_ib_cont_pages() and mlx5_ib_get_buf_offset() pairing which would reject valid configurations rather than adjust the page_size to make it work. In turn this is much more aggressive about choosing large page sizes for these objects and when THP is enabled it will now often find a single page solution. Link: https://lore.kernel.org/r/20201115114311.136250-2-leon@kernel.org Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-09-11RDMA/mlx4: Use ib_umem_num_dma_blocks()Jason Gunthorpe1-2/+0
For the calls linked to mlx4_ib_umem_calc_optimal_mtt_size() use ib_umem_num_dma_blocks() inside the function, it is just some weird static default. All other places are just using it with PAGE_SIZE, switch to ib_umem_num_dma_blocks(). As this is the last call site, remove ib_umem_num_count(). Link: https://lore.kernel.org/r/15-v2-270386b7e60b+28f4-umem_1_jgg@nvidia.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-09-11RDMA/umem: Split ib_umem_num_pages() into ib_umem_num_dma_blocks()Jason Gunthorpe1-3/+12
ib_umem_num_pages() should only be used by things working with the SGL in CPU pages directly. Drivers building DMA lists should use the new ib_num_dma_blocks() which returns the number of blocks rdma_umem_for_each_block() will return. To make this general for DMA drivers requires a different implementation. Computing DMA block count based on umem->address only works if the requested page size is < PAGE_SIZE and/or the IOVA == umem->address. Instead the number of DMA pages should be computed in the IOVA address space, not umem->address. Thus the IOVA has to be stored inside the umem so it can be used for these calculations. For now set it to umem->address by default and fix it up if ib_umem_find_best_pgsz() was called. This allows drivers to be converted to ib_umem_num_dma_blocks() safely. Link: https://lore.kernel.org/r/6-v2-270386b7e60b+28f4-umem_1_jgg@nvidia.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-09-09RDMA/umem: Add rdma_umem_for_each_dma_block()Jason Gunthorpe1-0/+20
This helper does the same as rdma_for_each_block(), except it works on a umem. This simplifies most of the call sites. Link: https://lore.kernel.org/r/4-v2-270386b7e60b+28f4-umem_1_jgg@nvidia.com Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Acked-by: Shiraz Saleem <shiraz.saleem@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-08-31RDMA/umem: Fix signature of stub ib_umem_find_best_pgsz()Jason Gunthorpe1-4/+5
The original function returns unsigned long and 0 on failure. Fixes: 4a35339958f1 ("RDMA/umem: Add API to find best driver supported page size in an MR") Link: https://lore.kernel.org/r/0-v1-982a13cc5c6d+501ae-fix_best_pgsz_stub_jgg@nvidia.com Reviewed-by: Gal Pressman <galpress@amazon.com> Acked-by: Shiraz Saleem <shiraz.saleem@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-07-29RDMA/include: Replace license text with SPDX tagsLeon Romanovsky1-28/+1
The header files in RDMA subsystem are dual licensed and can be described by simple SPDX tag, so replace all of them at once together with making them use the same coding style for header guard defines. Link: https://lore.kernel.org/r/20200719072521.135260-1-leon@kernel.org Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-01-16IB: Allow calls to ib_umem_get from kernel ULPsMoni Shoua1-2/+2
So far the assumption was that ib_umem_get() and ib_umem_odp_get() are called from flows that start in UVERBS and therefore has a user context. This assumption restricts flows that are initiated by ULPs and need the service that ib_umem_get() provides. This patch changes ib_umem_get() and ib_umem_odp_get() to get IB device directly by relying on the fact that both UVERBS and ULPs sets that field correctly. Reviewed-by: Guy Levi <guyle@mellanox.com> Signed-off-by: Moni Shoua <monis@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
2019-11-17IB/umem: remove the dmasync argument to ib_umem_getChristoph Hellwig1-2/+2
The argument is always ignored, so remove it. Link: https://lore.kernel.org/r/20191113073214.9514-3-hch@lst.de Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com> Acked-by: Michal Kalderon <michal.kalderon@marvell.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2019-08-21RDMA/odp: remove ib_ucontext from ib_umemJason Gunthorpe1-1/+1
At this point the ucontext is only being stored to access the ib_device, so just store the ib_device directly instead. This is more natural and logical as the umem has nothing to do with the ucontext. Link: https://lore.kernel.org/r/20190806231548.25242-8-jgg@ziepe.ca Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2019-05-21RDMA/umem: Move page_shift from ib_umem to ib_odp_umemJason Gunthorpe1-15/+4
This value has always been set to PAGE_SHIFT in the core code, the only thing that does differently was the ODP path. Move the value into the ODP struct and still use it for ODP, but change all the non-ODP things to just use PAGE_SHIFT/PAGE_SIZE/PAGE_MASK directly. Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
2019-05-06RDMA/umem: Remove hugetlb flagShiraz Saleem1-1/+0
The drivers i40iw and bnxt_re no longer dependent on the hugetlb flag. So remove this flag from ib_umem structure. Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com> Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2019-05-06RDMA/umem: Add API to find best driver supported page size in an MRShiraz Saleem1-0/+9
This helper iterates through the SG list to find the best page size to use from a bitmap of HW supported page sizes. Drivers that support multiple page sizes, but not mixed sizes in an MR can use this API. Suggested-by: Jason Gunthorpe <jgg@ziepe.ca> Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2019-04-08RDMA/umem: Combine contiguous PAGE_SIZE regions in SGEsShiraz Saleem1-1/+1
Combine contiguous regions of PAGE_SIZE pages into single scatter list entry while building the scatter table for a umem. This minimizes the number of the entries in the scatter list and reduces the DMA mapping overhead, particularly with the IOMMU. Set default max_seg_size in core for IB devices to 2G and do not combine if we exceed this limit. Also, purge npages in struct ib_umem as we now DMA map the umem SGL with sg_nents and npage computation is not needed. Drivers should now be using ib_umem_num_pages(), so fix the last stragglers. Move npages tracking to ib_umem_odp as ODP drivers still need it. Suggested-by: Jason Gunthorpe <jgg@ziepe.ca> Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Acked-by: Adit Ranadive <aditr@vmware.com> Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com> Tested-by: Gal Pressman <galpress@amazon.com> Tested-by: Selvin Xavier <selvin.xavier@broadcom.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2019-01-10IB/{core,hw}: Have ib_umem_get extract the ib_ucontext from ib_udataJason Gunthorpe1-3/+5
ib_umem_get() can only be called in a method callback, which always has a udata parameter. This allows ib_umem_get() to derive the ucontext pointer directly from the udata without requiring the drivers to find it in some way or another. Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
2018-09-21RDMA/umem: Get rid of struct ib_umem.odp_dataJason Gunthorpe1-3/+3
This no longer has any use, we can use container_of to get to the umem_odp, and a simple flag to indicate if this is an odp MR. Remove the few remaining references to it. Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
2018-09-20RDMA/umem: Do not use current->tgid to track the mm_structJason Gunthorpe1-2/+1
This is just wrong, the process that calls into the reg_mr is the process associated with the umem, and that does not have to be the same process that created the context. When this code was first written mmgrab() didn't exist, however these days we can just directly hold the mm_struct pointer in the umem and have no ambiguity when it comes to releasing the umem as to which mm it was associated with. Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
2018-05-15IB/umem: Use the correct mm during ib_umem_releaseLidong Chen1-1/+0
User-space may invoke ibv_reg_mr and ibv_dereg_mr in different threads. If ibv_dereg_mr is called after the thread which invoked ibv_reg_mr has exited, get_pid_task will return NULL and ib_umem_release will not decrease mm->pinned_vm. Instead of using threads to locate the mm, use the overall tgid from the ib_ucontext struct instead. This matches the behavior of ODP and disassociate in handling the mm of the process that called ibv_reg_mr. Cc: <stable@vger.kernel.org> Fixes: 87773dd56d54 ("IB: ib_umem_release() should decrement mm->pinned_vm from ib_umem_get") Signed-off-by: Lidong Chen <lidongchen@tencent.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2017-04-25IB/umem: Add contiguous ODP supportArtemy Kovalyov1-2/+2
Currenlty ODP supports only regular MMU pages. Add ODP support for regions consisting of physically contiguous chunks of arbitrary order (huge pages for instance) to improve performance. Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com> Signed-off-by: Leon Romanovsky <leon@kernel.org> Signed-off-by: Doug Ledford <dledford@redhat.com>
2017-04-25IB: Replace ib_umem page_size by page_shiftArtemy Kovalyov1-2/+2
Size of pages are held by struct ib_umem in page_size field. It is better to store it as an exponent, because page size by nature is always power-of-two and used as a factor, divisor or ilog2's argument. The conversion of page_size to be page_shift allows to have portable code and avoid following error while compiling on ARM: ERROR: "__aeabi_uldivmod" [drivers/infiniband/core/ib_core.ko] undefined! CC: Selvin Xavier <selvin.xavier@broadcom.com> CC: Steve Wise <swise@chelsio.com> CC: Lijun Ou <oulijun@huawei.com> CC: Shiraz Saleem <shiraz.saleem@intel.com> CC: Adit Ranadive <aditr@vmware.com> CC: Dennis Dalessandro <dennis.dalessandro@intel.com> CC: Ram Amrani <Ram.Amrani@Cavium.com> Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com> Signed-off-by: Leon Romanovsky <leon@kernel.org> Acked-by: Ram Amrani <Ram.Amrani@cavium.com> Acked-by: Shiraz Saleem <shiraz.saleem@intel.com> Acked-by: Selvin Xavier <selvin.xavier@broadcom.com> Acked-by: Selvin Xavier <selvin.xavier@broadcom.com> Acked-by: Adit Ranadive <aditr@vmware.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
2014-12-15IB/core: Add support for on demand paging regionsShachar Raindel1-0/+2
* Extend the umem struct to keep the ODP related data. * Allocate and initialize the ODP related information in the umem (page_list, dma_list) and freeing as needed in the end of the run. * Store a reference to the process PID struct in the ucontext. Used to safely obtain the task_struct and the mm during fault handling, without preventing the task destruction if needed. * Add 2 helper functions: ib_umem_odp_map_dma_pages and ib_umem_odp_unmap_dma_pages. These functions get the DMA addresses of specific pages of the umem (and, currently, pin them). * Support for page faults only - IB core will keep the reference on the pages used and call put_page when freeing an ODP umem area. Invalidations support will be added in a later patch. Signed-off-by: Sagi Grimberg <sagig@mellanox.com> Signed-off-by: Shachar Raindel <raindel@mellanox.com> Signed-off-by: Haggai Eran <haggaie@mellanox.com> Signed-off-by: Majd Dibbiny <majd@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
2014-12-15IB/mlx5: Add function to read WQE from user-spaceHaggai Eran1-1/+4
Add a helper function mlx5_ib_read_user_wqe to read information from user-space owned work queues. The function will be used in a later patch by the page-fault handling code in mlx5_ib. Signed-off-by: Haggai Eran <haggaie@mellanox.com> [ Add stub for ib_umem_copy_from() for CONFIG_INFINIBAND_USER_MEM=n - Roland ] Signed-off-by: Roland Dreier <roland@purestorage.com>
2014-12-15IB/core: Add umem function to read data from user-spaceHaggai Eran1-0/+2
In some drivers there's a need to read data from a user space area that was pinned using ib_umem when running from a different process context. The ib_umem_copy_from function allows reading data from the physical pages pinned in the ib_umem struct. Signed-off-by: Haggai Eran <haggaie@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
2014-12-15IB/core: Replace ib_umem's offset field with a full addressHaggai Eran1-1/+24
In order to allow umems that do not pin memory, we need the umem to keep track of its region's address. This makes the offset field redundant, and so this patch removes it. Signed-off-by: Haggai Eran <haggaie@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
2014-09-19IB: ib_umem_release() should decrement mm->pinned_vm from ib_umem_getShawn Bohrer1-0/+1
In debugging an application that receives -ENOMEM from ib_reg_mr(), I found that ib_umem_get() can fail because the pinned_vm count has wrapped causing it to always be larger than the lock limit even with RLIMIT_MEMLOCK set to RLIM_INFINITY. The wrapping of pinned_vm occurs because the process that calls ib_reg_mr() will have its mm->pinned_vm count incremented. Later a different process with a different mm_struct than the one that allocated the ib_umem struct ends up releasing it which results in decrementing the new processes mm->pinned_vm count past zero and wrapping. I'm not entirely sure what circumstances cause a different process to release the ib_umem than the one that allocated it but the kernel stack trace of the freeing process from my situation looks like the following: Call Trace: [<ffffffff814d64b1>] dump_stack+0x19/0x1b [<ffffffffa0b522a5>] ib_umem_release+0x1f5/0x200 [ib_core] [<ffffffffa0b90681>] mlx4_ib_destroy_qp+0x241/0x440 [mlx4_ib] [<ffffffffa0b4d93c>] ib_destroy_qp+0x12c/0x170 [ib_core] [<ffffffffa0cc7129>] ib_uverbs_close+0x259/0x4e0 [ib_uverbs] [<ffffffff81141cba>] __fput+0xba/0x240 [<ffffffff81141e4e>] ____fput+0xe/0x10 [<ffffffff81060894>] task_work_run+0xc4/0xe0 [<ffffffff810029e5>] do_notify_resume+0x95/0xa0 [<ffffffff814e3dd0>] int_signal+0x12/0x17 The following patch fixes the issue by storing the pid struct of the process that calls ib_umem_get() so that ib_umem_release and/or ib_umem_account() can properly decrement the pinned_vm count of the correct mm_struct. Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com> Reviewed-by: Shachar Raindel <raindel@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
2014-03-04IB: Refactor umem to use linear SG tableYishai Hadas1-8/+3
This patch refactors the IB core umem code and vendor drivers to use a linear (chained) SG table instead of chunk list. With this change the relevant code becomes clearer—no need for nested loops to build and use umem. Signed-off-by: Shachar Raindel <raindel@mellanox.com> Signed-off-by: Yishai Hadas <yishaih@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
2008-04-29IB: expand ib_umem_get() prototypeArthur Kepner1-2/+2
Add a new parameter, dmasync, to the ib_umem_get() prototype. Use dmasync = 1 when mapping user-allocated CQs with ib_umem_get(). Signed-off-by: Arthur Kepner <akepner@sgi.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Jesse Barnes <jbarnes@virtuousgeek.org> Cc: Jes Sorensen <jes@sgi.com> Cc: Randy Dunlap <randy.dunlap@oracle.com> Cc: Roland Dreier <rdreier@cisco.com> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: David Miller <davem@davemloft.net> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Grant Grundler <grundler@parisc-linux.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-09IB/umem: Add hugetlb flag to struct ib_umemJoachim Fenkes1-0/+1
During ib_umem_get(), determine whether all pages from the memory region are hugetlb pages and report this in the "hugetlb" member. Low-level drivers can use this information if they need it. Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com> Signed-off-by: Roland Dreier <rolandd@cisco.com>
2007-05-21Detach sched.h from mm.hAlexey Dobriyan1-0/+1
First thing mm.h does is including sched.h solely for can_do_mlock() inline function which has "current" dereference inside. By dealing with can_do_mlock() mm.h can be detached from sched.h which is good. See below, why. This patch a) removes unconditional inclusion of sched.h from mm.h b) makes can_do_mlock() normal function in mm/mlock.c c) exports can_do_mlock() to not break compilation d) adds sched.h inclusions back to files that were getting it indirectly. e) adds less bloated headers to some files (asm/signal.h, jiffies.h) that were getting them indirectly Net result is: a) mm.h users would get less code to open, read, preprocess, parse, ... if they don't need sched.h b) sched.h stops being dependency for significant number of files: on x86_64 allmodconfig touching sched.h results in recompile of 4083 files, after patch it's only 3744 (-8.3%). Cross-compile tested on all arm defconfigs, all mips defconfigs, all powerpc defconfigs, alpha alpha-up arm i386 i386-up i386-defconfig i386-allnoconfig ia64 ia64-up m68k mips parisc parisc-up powerpc powerpc-up s390 s390-up sparc sparc-up sparc64 sparc64-up um-x86_64 x86_64 x86_64-up x86_64-defconfig x86_64-allnoconfig as well as my two usual configs. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-08IB: Put rlimit accounting struct in struct ib_umemRoland Dreier1-0/+3
When memory pinned with ib_umem_get() is released, ib_umem_release() needs to subtract the amount of memory being unpinned from mm->locked_vm. However, ib_umem_release() may be called with mm->mmap_sem already held for writing if the memory is being released as part of an munmap() call, so it is sometimes necessary to defer this accounting into a workqueue. However, the work struct used to defer this accounting is dynamically allocated before it is queued, so there is the possibility of failing that allocation. If the allocation fails, then ib_umem_release has no choice except to bail out and leave the process with a permanently elevated locked_vm. Fix this by allocating the structure to defer accounting as part of the original struct ib_umem, so there's no possibility of failing a later allocation if creating the struct ib_umem and pinning memory succeeds. Signed-off-by: Roland Dreier <rolandd@cisco.com>
2007-05-08IB/uverbs: Export ib_umem_get()/ib_umem_release() to modulesRoland Dreier1-0/+78
Export ib_umem_get()/ib_umem_release() and put low-level drivers in control of when to call ib_umem_get() to pin and DMA map userspace, rather than always calling it in ib_uverbs_reg_mr() before calling the low-level driver's reg_user_mr method. Also move these functions to be in the ib_core module instead of ib_uverbs, so that driver modules using them do not depend on ib_uverbs. This has a number of advantages: - It is better design from the standpoint of making generic code a library that can be used or overridden by device-specific code as the details of specific devices dictate. - Drivers that do not need to pin userspace memory regions do not need to take the performance hit of calling ib_mem_get(). For example, although I have not tried to implement it in this patch, the ipath driver should be able to avoid pinning memory and just use copy_{to,from}_user() to access userspace memory regions. - Buffers that need special mapping treatment can be identified by the low-level driver. For example, it may be possible to solve some Altix-specific memory ordering issues with mthca CQs in userspace by mapping CQ buffers with extra flags. - Drivers that need to pin and DMA map userspace memory for things other than memory regions can use ib_umem_get() directly, instead of hacks using extra parameters to their reg_phys_mr method. For example, the mlx4 driver that is pending being merged needs to pin and DMA map QP and CQ buffers, but it does not need to create a memory key for these buffers. So the cleanest solution is for mlx4 to call ib_umem_get() in the create_qp and create_cq methods. Signed-off-by: Roland Dreier <rolandd@cisco.com>