IB/uverbs: Export ib_umem_get()/ib_umem_release() to modules

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>

2 files changed, 21 insertions, 8 deletions

diff --git a/drivers/infiniband/hw/cxgb3/iwch_provider.c b/drivers/infiniband/hw/cxgb3/iwch_provider.c
index a891493fd340..e7c2c3948037 100644
--- a/drivers/infiniband/hw/cxgb3/iwch_provider.c
+++ b/drivers/infiniband/hw/cxgb3/iwch_provider.c
@@ -47,6 +47,7 @@
 #include <rdma/iw_cm.h>
 #include <rdma/ib_verbs.h>
 #include <rdma/ib_smi.h>
+#include <rdma/ib_umem.h>
 #include <rdma/ib_user_verbs.h>
 
 #include "cxio_hal.h"
@@ -443,6 +444,8 @@ static int iwch_dereg_mr(struct ib_mr *ib_mr)
         remove_handle(rhp, &rhp->mmidr, mmid);
         if (mhp->kva)
                 kfree((void *) (unsigned long) mhp->kva);
+        if (mhp->umem)
+                ib_umem_release(mhp->umem);
         PDBG("%s mmid 0x%x ptr %p\n", __FUNCTION__, mmid, mhp);
         kfree(mhp);
         return 0;
@@ -577,8 +580,8 @@ static int iwch_reregister_phys_mem(struct ib_mr *mr,
 }
 
 
-static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, struct ib_umem *region,
-                                      int acc, struct ib_udata *udata)
+static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
+                                      u64 virt, int acc, struct ib_udata *udata)
 {
         __be64 *pages;
         int shift, n, len;
@@ -591,7 +594,6 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, struct ib_umem *region,
         struct iwch_reg_user_mr_resp uresp;
 
         PDBG("%s ib_pd %p\n", __FUNCTION__, pd);
-        shift = ffs(region->page_size) - 1;
 
         php = to_iwch_pd(pd);
         rhp = php->rhp;
@@ -599,8 +601,17 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, struct ib_umem *region,
         if (!mhp)
                 return ERR_PTR(-ENOMEM);
 
+        mhp->umem = ib_umem_get(pd->uobject->context, start, length, acc);
+        if (IS_ERR(mhp->umem)) {
+                err = PTR_ERR(mhp->umem);
+                kfree(mhp);
+                return ERR_PTR(err);
+        }
+
+        shift = ffs(mhp->umem->page_size) - 1;
+
         n = 0;
-        list_for_each_entry(chunk, &region->chunk_list, list)
+        list_for_each_entry(chunk, &mhp->umem->chunk_list, list)
                 n += chunk->nents;
 
         pages = kmalloc(n * sizeof(u64), GFP_KERNEL);
@@ -611,13 +622,13 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, struct ib_umem *region,
 
         i = n = 0;
 
-        list_for_each_entry(chunk, &region->chunk_list, list)
+        list_for_each_entry(chunk, &mhp->umem->chunk_list, list)
                 for (j = 0; j < chunk->nmap; ++j) {
                         len = sg_dma_len(&chunk->page_list[j]) >> shift;
                         for (k = 0; k < len; ++k) {
                                 pages[i++] = cpu_to_be64(sg_dma_address(
                                         &chunk->page_list[j]) +
-                                        region->page_size * k);
+                                        mhp->umem->page_size * k);
                         }
                 }
 
@@ -625,9 +636,9 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, struct ib_umem *region,
         mhp->attr.pdid = php->pdid;
         mhp->attr.zbva = 0;
         mhp->attr.perms = iwch_ib_to_tpt_access(acc);
-        mhp->attr.va_fbo = region->virt_base;
+        mhp->attr.va_fbo = virt;
         mhp->attr.page_size = shift - 12;
-        mhp->attr.len = (u32) region->length;
+        mhp->attr.len = (u32) length;
         mhp->attr.pbl_size = i;
         err = iwch_register_mem(rhp, php, mhp, shift, pages);
         kfree(pages);
@@ -650,6 +661,7 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, struct ib_umem *region,
         return &mhp->ibmr;
 
 err:
+        ib_umem_release(mhp->umem);
         kfree(mhp);
         return ERR_PTR(err);
 }
diff --git a/drivers/infiniband/hw/cxgb3/iwch_provider.h b/drivers/infiniband/hw/cxgb3/iwch_provider.h
index 93bcc56756bd..48833f3f3bd0 100644
--- a/drivers/infiniband/hw/cxgb3/iwch_provider.h
+++ b/drivers/infiniband/hw/cxgb3/iwch_provider.h
@@ -73,6 +73,7 @@ struct tpt_attributes {
 
 struct iwch_mr {
         struct ib_mr ibmr;
+        struct ib_umem *umem;
         struct iwch_dev *rhp;
         u64 kva;
         struct tpt_attributes attr;