4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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)