[PATCH] powerpc/powernv: Get more flushing requirements from device-tree

[Russell Currey]

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

Since commit 84ed26fd00c5 ("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.

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 fixes that too.

Reported-by: Joel Stanley <joel at jms.id.au>
Signed-off-by: Russell Currey <ruscur at russell.cc>
---
 arch/powerpc/platforms/powernv/setup.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 105d889abd51..824c3ad7a0fa 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -96,6 +96,15 @@ 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);
+
+	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)
-- 
2.35.1