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    Subject[PATCH v2 2/4] libnvdimm/namespace: Enforce memremap_compat_align()
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    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.kumar@linux.ibm.com>
    Cc: Jeff Moyer <jmoyer@redhat.com>
    Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
    Link: https://lore.kernel.org/r/158041477336.3889308.4581652885008605170.stgit@dwillia2-desk3.amr.corp.intel.com
    Signed-off-by: Dan Williams <dan.j.williams@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;

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