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powerpc/powernv: Get STF barrier requirements from device-tree 

The device-tree property no-need-store-drain-on-priv-state-switch is
equivalent to H_CPU_BEHAV_NO_STF_BARRIER from the
H_CPU_GET_CHARACTERISTICS hcall on pseries.

Since commit 84ed26fd00 ("powerpc/security: Add a security feature for
STF barrier") powernv systems with this device-tree property have been
enabling the STF barrier when they have no need for it.  This patch
fixes this by clearing the STF barrier feature on those systems.

Fixes: 84ed26fd00 ("powerpc/security: Add a security feature for STF barrier")
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/20220404101536.104794-2-ruscur@russell.cc
This commit is contained in:
Russell Currey 2022-04-04 20:15:36 +10:00 committed by Michael Ellerman
parent 2efee6adb5
commit d2a3c13198
1 changed files with 3 additions and 0 deletions
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3
arch/powerpc/platforms/powernv/setup.c
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@ -102,6 +102,9 @@ static void __init init_fw_feat_flags(struct device_node *np)
if (fw_feature_is("enabled", "no-need-l1d-flush-kernel-on-user-access", np))
security_ftr_clear(SEC_FTR_L1D_FLUSH_UACCESS);
if (fw_feature_is("enabled", "no-need-store-drain-on-priv-state-switch", np))
security_ftr_clear(SEC_FTR_STF_BARRIER);
}
static void __init pnv_setup_security_mitigations(void)