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From:   Jeff Moyer <jmoyer@redhat.com>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     linux-nvdimm@lists.01.org,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        vishal.l.verma@intel.com, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 2/4] libnvdimm/namespace: Enforce memremap_compat_align()
References: <158155489850.3343782.2687127373754434980.stgit@dwillia2-desk3.amr.corp.intel.com>
        <158155490897.3343782.14216276134794923581.stgit@dwillia2-desk3.amr.corp.intel.com>
Date:   Thu, 13 Feb 2020 14:16:00 -0500
In-Reply-To: <158155490897.3343782.14216276134794923581.stgit@dwillia2-desk3.amr.corp.intel.com>
        (Dan Williams's message of "Wed, 12 Feb 2020 16:48:29 -0800")
Message-ID: <x49o8u25mdr.fsf@segfault.boston.devel.redhat.com>
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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>

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>