4.14-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/memory.h> #include <linux/nmi.h> +#include <asm/debugfs.h> #include <asm/io.h> #include <asm/kdump.h> #include <asm/prom.h> @@ -885,6 +886,35 @@ 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)