[PATCH v2 2/4] libnvdimm/namespace: Enforce memremap_compat_align()

[Dan Williams]

The pmem driver on PowerPC crashes with the following signature when
instantiating misaligned namespaces that map their capacity via
memremap_pages().

    BUG: Unable to handle kernel data access at 0xc001000406000000
    Faulting instruction address: 0xc000000000090790
    NIP [c000000000090790] arch_add_memory+0xc0/0x130
    LR [c000000000090744] arch_add_memory+0x74/0x130
    Call Trace:
     arch_add_memory+0x74/0x130 (unreliable)
     memremap_pages+0x74c/0xa30
     devm_memremap_pages+0x3c/0xa0
     pmem_attach_disk+0x188/0x770
     nvdimm_bus_probe+0xd8/0x470

With the assumption that only memremap_pages() has alignment
constraints, enforce memremap_compat_align() for
pmem_should_map_pages(), nd_pfn, or nd_dax cases.

Reported-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Cc: Jeff Moyer <jmo...@redhat.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Link: 
https://lore.kernel.org/r/158041477336.3889308.4581652885008605170.st...@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/nvdimm/namespace_devs.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 032dc61725ff..aff1f32fdb4f 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -1739,6 +1739,16 @@ struct nd_namespace_common 
*nvdimm_namespace_common_probe(struct device *dev)
                return ERR_PTR(-ENODEV);
        }
 
+       if (pmem_should_map_pages(dev) || nd_pfn || nd_dax) {
+               struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
+               resource_size_t start = nsio->res.start;
+
+               if (!IS_ALIGNED(start | size, memremap_compat_align())) {
+                       dev_dbg(&ndns->dev, "misaligned, unable to map\n");
+                       return ERR_PTR(-EOPNOTSUPP);
+               }
+       }
+
        if (is_namespace_pmem(&ndns->dev)) {
                struct nd_namespace_pmem *nspm;