linux-kernel - [PATCH RFC rebase 9/9] powerpc/64: barrier

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Date:   Thu, 15 Mar 2018 20:15:58 +0100
From:   Michal Suchanek <msuchanek@...e.de>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     Kate Stewart <kstewart@...uxfoundation.org>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Neuling <mikey@...ling.org>,
        "Bryant G. Ly" <bryantly@...ux.vnet.ibm.com>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Daniel Axtens <dja@...ens.net>,
        Nicholas Piggin <npiggin@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Gibson <david@...son.dropbear.id.au>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Cédric Le Goater <clg@...d.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Joe Perches <joe@...ches.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Tobin C. Harding" <me@...in.cc>,
        Michal Suchanek <msuchanek@...e.de>
Subject: [PATCH RFC rebase 9/9] powerpc/64: barrier_nospec: Add commandline trigger

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@...e.de>
---
 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