[PATCH RFC rebase 9/9] powerpc/64: barrier_nospec: Add commandline trigger

[Michal Suchanek]

Add commandline options spectre_v2 and nospectre_v2

These are named same as similar x86 options regardless of actual effect
to not require platform-specific configuration.

Supported options:
nospectre_v2 or spectre_v2=off - speculation barrier not used
spectre_v2=on or spectre_v2=auto - speculation barrier used

Changing the settings after boot is not supported and VM migration may
change requirements so auto is same as on.

Based on s390 implementation

Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
---
 arch/powerpc/kernel/setup_64.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index f6678a7b6114..c74e656265df 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -840,6 +840,28 @@ static int __init handle_no_pti(char *p)
 }
 early_param("nopti", handle_no_pti);
 
+static int __init nospectre_v2_setup_early(char *str)
+{
+	no_nospec = true;
+	return 0;
+}
+early_param("nospectre_v2", nospectre_v2_setup_early);
+
+static int __init spectre_v2_setup_early(char *str)
+{
+	if (str && !strncmp(str, "on", 2))
+		no_nospec = false;
+
+	if (str && !strncmp(str, "off", 3))
+		no_nospec = true;
+
+	if (str && !strncmp(str, "auto", 4))
+		no_nospec = false;
+
+	return 0;
+}
+early_param("spectre_v2", spectre_v2_setup_early);
+
 static void do_nothing(void *unused)
 {
 	/*
-- 
2.13.6