linux-kernel - [PATCH 5.17 546/772] powerpc/powernv: Get L1D flush requirements from device-tree

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Date:   Tue,  7 Jun 2022 19:02:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joel Stanley <joel@....id.au>,
        Russell Currey <ruscur@...sell.cc>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 546/772] powerpc/powernv: Get L1D flush requirements from device-tree

From: Russell Currey <ruscur@...sell.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@....id.au>
Signed-off-by: Russell Currey <ruscur@...sell.cc>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20220404101536.104794-1-ruscur@russell.cc
Signed-off-by: Sasha Levin <sashal@...nel.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