[PATCH RFC 3/5] powerpc/speculation: Add support for 'cpu_spec_mitigations=' cmdline options

[Josh Poimboeuf <jpoimboe@redhat.com>]

Configure powerpc CPU runtime speculation bug mitigations in accordance
with the 'cpu_spec_mitigations=' cmdline options.  This affects
Meltdown, Spectre v1, Spectre v2, and Speculative Store Bypass.

The default behavior is unchanged.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 9 +++++----
 arch/powerpc/kernel/security.c                  | 6 +++---
 arch/powerpc/kernel/setup_64.c                  | 2 +-
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 29dc03971630..0e8eae1e8a25 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2552,10 +2552,11 @@
 
 			off
 				Disable all speculative CPU mitigations.
-				Equivalent to: nopti [x86]
+				Equivalent to: nopti [x86, powerpc]
+					       nospectre_v1 [powerpc]
 					       nospectre_v2 [x86]
 					       spectre_v2_user=off [x86]
-					       spec_store_bypass_disable=off [x86]
+					       spec_store_bypass_disable=off [x86, powerpc]
 					       l1tf=off [x86]
 
 			auto (default)
@@ -2568,7 +2569,7 @@
 				Equivalent to: pti=auto [x86]
 					       spectre_v2=auto [x86]
 					       spectre_v2_user=auto [x86]
-					       spec_store_bypass_disable=auto [x86]
+					       spec_store_bypass_disable=auto [x86, powerpc]
 					       l1tf=flush [x86]
 
 			auto,nosmt
@@ -2579,7 +2580,7 @@
 				Equivalent to: pti=auto [x86]
 					       spectre_v2=auto [x86]
 					       spectre_v2_user=auto [x86]
-					       spec_store_bypass_disable=auto [x86]
+					       spec_store_bypass_disable=auto [x86, powerpc]
 					       l1tf=flush,nosmt [x86]
 
 	mminit_loglevel=
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index b33bafb8fcea..5aed4ad729ba 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -57,7 +57,7 @@ void setup_barrier_nospec(void)
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 		 security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
 
-	if (!no_nospec)
+	if (!no_nospec && cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
 		enable_barrier_nospec(enable);
 }
 
@@ -116,7 +116,7 @@ static int __init handle_nospectre_v2(char *p)
 early_param("nospectre_v2", handle_nospectre_v2);
 void setup_spectre_v2(void)
 {
-	if (no_spectrev2)
+	if (no_spectrev2 || cpu_spec_mitigations == CPU_SPEC_MITIGATIONS_OFF)
 		do_btb_flush_fixups();
 	else
 		btb_flush_enabled = true;
@@ -300,7 +300,7 @@ void setup_stf_barrier(void)
 
 	stf_enabled_flush_types = type;
 
-	if (!no_stf_barrier)
+	if (!no_stf_barrier && cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
 		stf_barrier_enable(enable);
 }
 
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index ba404dd9ce1d..d9d796a66a79 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -932,7 +932,7 @@ void setup_rfi_flush(enum l1d_flush_type types, bool enable)
 
 	enabled_flush_types = types;
 
-	if (!no_rfi_flush)
+	if (!no_rfi_flush || cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
 		rfi_flush_enable(enable);
 }
 
-- 
2.17.2