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    Subject[PATCH AUTOSEL 4.9 67/91] EDAC/ghes: Fix grain calculation
    Date
    From: Robert Richter <rrichter@marvell.com>

    [ Upstream commit 7088e29e0423d3195e09079b4f849ec4837e5a75 ]

    The current code to convert a physical address mask to a grain
    (defined as granularity in bytes) is:

    e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK);

    This is broken in several ways:

    1) It calculates to wrong grain values. E.g., a physical address mask
    of ~0xfff should give a grain of 0x1000. Without considering
    PAGE_MASK, there is an off-by-one. Things are worse when also
    filtering it with ~PAGE_MASK. This will calculate to a grain with the
    upper bits set. In the example it even calculates to ~0.

    2) The grain does not depend on and is unrelated to the kernel's
    page-size. The page-size only matters when unmapping memory in
    memory_failure(). Smaller grains are wrongly rounded up to the
    page-size, on architectures with a configurable page-size (e.g. arm64)
    this could round up to the even bigger page-size of the hypervisor.

    Fix this with:

    e->grain = ~mem_err->physical_addr_mask + 1;

    The grain_bits are defined as:

    grain = 1 << grain_bits;

    Change also the grain_bits calculation accordingly, it is the same
    formula as in edac_mc.c now and the code can be unified.

    The value in ->physical_addr_mask coming from firmware is assumed to
    be contiguous, but this is not sanity-checked. However, in case the
    mask is non-contiguous, a conversion to grain_bits effectively
    converts the grain bit mask to a power of 2 by rounding it up.

    Suggested-by: James Morse <james.morse@arm.com>
    Signed-off-by: Robert Richter <rrichter@marvell.com>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
    Cc: "linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>
    Cc: Tony Luck <tony.luck@intel.com>
    Link: https://lkml.kernel.org/r/20191106093239.25517-11-rrichter@marvell.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/edac/ghes_edac.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c
    index e3fa4390f8460..4ddbf6604e2ab 100644
    --- a/drivers/edac/ghes_edac.c
    +++ b/drivers/edac/ghes_edac.c
    @@ -189,6 +189,7 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev,
    /* Cleans the error report buffer */
    memset(e, 0, sizeof (*e));
    e->error_count = 1;
    + e->grain = 1;
    strcpy(e->label, "unknown label");
    e->msg = pvt->msg;
    e->other_detail = pvt->other_detail;
    @@ -284,7 +285,7 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev,

    /* Error grain */
    if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK)
    - e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK);
    + e->grain = ~mem_err->physical_addr_mask + 1;

    /* Memory error location, mapped on e->location */
    p = e->location;
    @@ -391,8 +392,13 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev,
    if (p > pvt->other_detail)
    *(p - 1) = '\0';

    + /* Sanity-check driver-supplied grain value. */
    + if (WARN_ON_ONCE(!e->grain))
    + e->grain = 1;
    +
    + grain_bits = fls_long(e->grain - 1);
    +
    /* Generate the trace event */
    - grain_bits = fls_long(e->grain);
    snprintf(pvt->detail_location, sizeof(pvt->detail_location),
    "APEI location: %s %s", e->location, e->other_detail);
    trace_mc_event(type, e->msg, e->label, e->error_count,
    --
    2.20.1
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