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Date: Mon, 8 Aug 2016 13:10:19 -0600
From: Ross Zwisler <ross.zwisler@...ux.intel.com>
To: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Dan Williams <dan.j.williams@...el.com>,
Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
linux-nvdimm@...ts.01.org, "Lee, Chun-Yi" <jlee@...e.com>,
stable@...r.kernel.org#v4.2+
Subject: Re: [PATCH v2] libnvdimm, nd_blk: mask off reserved status bits
On Tue, Aug 02, 2016 at 12:26:53PM -0600, Ross Zwisler wrote:
> The "NVDIMM Block Window Driver Writer's Guide":
>
> http://pmem.io/documents/
> http://pmem.io/documents/NVDIMM_DriverWritersGuide-July-2016.pdf
>
> defines the layout of the block window status register. For the July 2016
> version of the spec linked to above, this happens in Figure 4 on page 26.
>
> The only bits defined in this spec are bits 31, 5, 4, 2, 1 and 0. The rest
> of the bits in the status register are reserved, and there is a warning
> following the diagram that says:
>
> Note: The driver cannot assume the value of the RESERVED bits in the
> status register are zero. These reserved bits need to be masked off, and
> the driver must avoid checking the state of those bits.
>
> This change ensures that for hardware implementations that set these
> reserved bits in the status register, the driver won't incorrectly fail the
> block I/Os.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Reviewed-by: Lee, Chun-Yi <jlee@...e.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: stable@...r.kernel.org # v4.2+
Ping on this patch - through which tree should we merge this for v4.8-rc2?
Dan's nvdimm tree?
> ---
>
> Changes from V1:
> - Rebased onto the v4.8 merge tree. As Joey points out the ND BLK code
> recently moved from drivers/acpi/nfit.c to drivers/acpi/nfit/core.c.
> Since we were in the merge window for v4.8 I didn't know what to use as
> a baseline, so I just used v4.7, which was apparently incorrect. Sorry
> about that.
>
> - Added Joey's reviewed-by.
>
> For stable kernels v4.2 and beyond the v1 patch for drivers/acpi/nfit.c
> applies cleanly and should be used.
>
> ---
> drivers/acpi/nfit/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 8c234dd..80cc7c0 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -1527,11 +1527,12 @@ static u32 read_blk_stat(struct nfit_blk *nfit_blk, unsigned int bw)
> {
> struct nfit_blk_mmio *mmio = &nfit_blk->mmio[DCR];
> u64 offset = nfit_blk->stat_offset + mmio->size * bw;
> + const u32 STATUS_MASK = 0x80000037;
>
> if (mmio->num_lines)
> offset = to_interleave_offset(offset, mmio);
>
> - return readl(mmio->addr.base + offset);
> + return readl(mmio->addr.base + offset) & STATUS_MASK;
> }
>
> static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
> --
> 2.9.0
>
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