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on 2022/1/6 14:12, Li Zhijian wrote:

Add Dan to the party :)

May i know whether there is any existing APIs to check whether
a va/page backs to a nvdimm/pmem ?

On 06/01/2022 08:21, Jason Gunthorpe wrote:
On Tue, Dec 28, 2021 at 04:07:08PM +0800, Li Zhijian wrote:
We can use it to indicate whether the registering mr is associated with
a pmem/nvdimm or not.

Currently, we only assign it in rxe driver, for other device/drivers,
they should implement it if needed.

RDMA FLUSH will support the persistence feature for a pmem/nvdimm.

Signed-off-by: Li Zhijian <>
  drivers/infiniband/sw/rxe/rxe_mr.c | 47 ++++++++++++++++++++++++++++++
  include/rdma/ib_verbs.h            |  1 +
  2 files changed, 48 insertions(+)

diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index 7c4cd19a9db2..bcd5e7afa475 100644
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -162,6 +162,50 @@ void rxe_mr_init_dma(struct rxe_pd *pd, int access, struct rxe_mr *mr)
      mr->type = IB_MR_TYPE_DMA;
  +// XXX: the logic is similar with mm/memory-failure.c
+static bool page_in_dev_pagemap(struct page *page)
+    unsigned long pfn;
+    struct page *p;
+    struct dev_pagemap *pgmap = NULL;
+    pfn = page_to_pfn(page);
+    if (!pfn) {
+        pr_err("no such pfn for page %p\n", page);
+        return false;
+    }
+    p = pfn_to_online_page(pfn);
+    if (!p) {
+        if (pfn_valid(pfn)) {
+            pgmap = get_dev_pagemap(pfn, NULL);
+            if (pgmap)
+                put_dev_pagemap(pgmap);
+        }
+    }
+    return !!pgmap;
You need to get Dan to check this out, but I'm pretty sure this should
be more like this:

if (is_zone_device_page(page) && page->pgmap->type == MEMORY_DEVICE_FS_DAX)

Great, i have added him.

+static bool iova_in_pmem(struct rxe_mr *mr, u64 iova, int length)
+    struct page *page = NULL;
+    char *vaddr = iova_to_vaddr(mr, iova, length);
+    if (!vaddr) {
+        pr_err("not a valid iova %llu\n", iova);
+        return false;
+    }
+    page = virt_to_page(vaddr);
And obviously this isn't uniform for the entire umem, so I don't even
know what this is supposed to mean.

My intention is to check if a memory region belongs to a nvdimm/pmem.
The approach is like that:
iova(user space)-+                     +-> page -> page_in_dev_pagemap()
                 |                     |
                 +-> va(kernel space) -+
Since current MR's va is associated with map_set where it record the relations
between iova and va and page. Do do you mean we should travel map_set to
get its page ? or by any other ways.

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 6e9ad656ecb7..822ebb3425dc 100644
+++ b/include/rdma/ib_verbs.h
@@ -1807,6 +1807,7 @@ struct ib_mr {
      unsigned int       page_size;
      enum ib_mr_type       type;
      bool           need_inval;
+    bool           is_pmem;
Or why it is being stored in the global struct?

Indeed, it's not strong necessary. but i think is_pmem should belongs to a ib_mr so that it can be checked by other general code when they needed even though no
one does such checking so far.



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