powerpc/powernv: Get L1D flush requirements from device-tree

jira LE-1907
Rebuild_History Non-Buildable kernel-rt-5.14.0-284.30.1.rt14.315.el9_2
commit-author Russell Currey <ruscur@russell.cc>
commit 2efee6a

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 d02fa40 ("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: d02fa40 ("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

(cherry picked from commit 2efee6a)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

arch/powerpc/platforms/powernv/setup.c

@@ -96,6 +96,12 @@ static void 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 pnv_setup_security_mitigations(void)