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    Subject[PATCH 5.17 546/772] powerpc/powernv: Get L1D flush requirements from device-tree
    Date
    From: Russell Currey <ruscur@russell.cc>

    [ Upstream commit 2efee6adb56159288bce9d1ab51fc9056d7007d4 ]

    The device-tree properties no-need-l1d-flush-msr-pr-1-to-0 and
    no-need-l1d-flush-kernel-on-user-access are the equivalents of
    H_CPU_BEHAV_NO_L1D_FLUSH_ENTRY and H_CPU_BEHAV_NO_L1D_FLUSH_UACCESS
    from the H_GET_CPU_CHARACTERISTICS hcall on pseries respectively.

    In commit d02fa40d759f ("powerpc/powernv: Remove POWER9 PVR version
    check for entry and uaccess flushes") the condition for disabling the
    L1D flush on kernel entry and user access was changed from any non-P9
    CPU to only checking P7 and P8. Without the appropriate device-tree
    checks for newer processors on powernv, these flushes are unnecessarily
    enabled on those systems. This patch corrects this.

    Fixes: d02fa40d759f ("powerpc/powernv: Remove POWER9 PVR version check for entry and uaccess flushes")
    Reported-by: Joel Stanley <joel@jms.id.au>
    Signed-off-by: Russell Currey <ruscur@russell.cc>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20220404101536.104794-1-ruscur@russell.cc
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/platforms/powernv/setup.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
    index 105d889abd51..378f7e5f18d2 100644
    --- a/arch/powerpc/platforms/powernv/setup.c
    +++ b/arch/powerpc/platforms/powernv/setup.c
    @@ -96,6 +96,12 @@ static void __init init_fw_feat_flags(struct device_node *np)

    if (fw_feature_is("disabled", "needs-spec-barrier-for-bound-checks", np))
    security_ftr_clear(SEC_FTR_BNDS_CHK_SPEC_BAR);
    +
    + if (fw_feature_is("enabled", "no-need-l1d-flush-msr-pr-1-to-0", np))
    + security_ftr_clear(SEC_FTR_L1D_FLUSH_ENTRY);
    +
    + if (fw_feature_is("enabled", "no-need-l1d-flush-kernel-on-user-access", np))
    + security_ftr_clear(SEC_FTR_L1D_FLUSH_UACCESS);
    }

    static void __init pnv_setup_security_mitigations(void)
    --
    2.35.1


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