linux-kernel - [PATCH 4.4 016/108] powerpc/64s: Allow control of RFI flush via debugfs

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Date:   Thu, 15 Feb 2018 16:16:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Subject: [PATCH 4.4 016/108] powerpc/64s: Allow control of RFI flush via debugfs

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Ellerman <mpe@...erman.id.au>

commit 236003e6b5443c45c18e613d2b0d776a9f87540e upstream.

Expose the state of the RFI flush (enabled/disabled) via debugfs, and
allow it to be enabled/disabled at runtime.

eg: $ cat /sys/kernel/debug/powerpc/rfi_flush
    1
    $ echo 0 > /sys/kernel/debug/powerpc/rfi_flush
    $ cat /sys/kernel/debug/powerpc/rfi_flush
    0

Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Reviewed-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kernel/setup_64.c |   30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -38,6 +38,7 @@
 #include <linux/hugetlb.h>
 #include <linux/memory.h>
 #include <linux/nmi.h>
+#include <linux/debugfs.h>
 
 #include <asm/io.h>
 #include <asm/kdump.h>
@@ -935,6 +936,35 @@ void __init setup_rfi_flush(enum l1d_flu
 		rfi_flush_enable(enable);
 }
 
+#ifdef CONFIG_DEBUG_FS
+static int rfi_flush_set(void *data, u64 val)
+{
+	if (val == 1)
+		rfi_flush_enable(true);
+	else if (val == 0)
+		rfi_flush_enable(false);
+	else
+		return -EINVAL;
+
+	return 0;
+}
+
+static int rfi_flush_get(void *data, u64 *val)
+{
+	*val = rfi_flush ? 1 : 0;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_rfi_flush, rfi_flush_get, rfi_flush_set, "%llu\n");
+
+static __init int rfi_flush_debugfs_init(void)
+{
+	debugfs_create_file("rfi_flush", 0600, powerpc_debugfs_root, NULL, &fops_rfi_flush);
+	return 0;
+}
+device_initcall(rfi_flush_debugfs_init);
+#endif
+
 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	if (rfi_flush)