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SubjectRe: [PATCH v2 2/4] libnvdimm/namespace: Enforce memremap_compat_align()
Date
Dan Williams <dan.j.williams@intel.com> writes:

> 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;
>

Actually, I take back my ack. :) This prevents a previously working
namespace from being successfully probed/setup. I thought we were only
going to enforce the alignment for a newly created namespace? This should
only check whether the alignment works for the current platform.

-Jeff

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