Commit ae082ed4 authored by Michal Suchanek's avatar Michal Suchanek Committed by Greg Kroah-Hartman

powerpc/64s: Enable barrier_nospec based on firmware settings

commit cb3d6759 upstream.

Check what firmware told us and enable/disable the barrier_nospec as

We err on the side of enabling the barrier, as it's no-op on older
systems, see the comment for more detail.
Signed-off-by: 's avatarMichael Ellerman <>
Signed-off-by: 's avatarGreg Kroah-Hartman <>
parent 31c3a1e8
......@@ -52,6 +52,7 @@ enum l1d_flush_type {
void setup_rfi_flush(enum l1d_flush_type, bool enable);
void do_rfi_flush_fixups(enum l1d_flush_type types);
void setup_barrier_nospec(void);
void do_barrier_nospec_fixups(bool enable);
extern bool barrier_nospec_enabled;
......@@ -23,6 +23,65 @@ static void enable_barrier_nospec(bool enable)
void setup_barrier_nospec(void)
bool enable;
* It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
* But there's a good reason not to. The two flags we check below are
* both are enabled by default in the kernel, so if the hcall is not
* functional they will be enabled.
* On a system where the host firmware has been updated (so the ori
* functions as a barrier), but on which the hypervisor (KVM/Qemu) has
* not been updated, we would like to enable the barrier. Dropping the
* check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
* we potentially enable the barrier on systems where the host firmware
* is not updated, but that's harmless as it's a no-op.
enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
static int barrier_nospec_set(void *data, u64 val)
switch (val) {
case 0:
case 1:
return -EINVAL;
if (!!val == !!barrier_nospec_enabled)
return 0;
return 0;
static int barrier_nospec_get(void *data, u64 *val)
*val = barrier_nospec_enabled ? 1 : 0;
return 0;
barrier_nospec_get, barrier_nospec_set, "%llu\n");
static __init int barrier_nospec_debugfs_init(void)
debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
return 0;
#endif /* CONFIG_DEBUG_FS */
ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
bool thread_priv;
......@@ -123,6 +123,7 @@ static void pnv_setup_rfi_flush(void)
setup_rfi_flush(type, enable);
static void __init pnv_setup_arch(void)
......@@ -534,6 +534,7 @@ void pseries_setup_rfi_flush(void)
setup_rfi_flush(types, enable);
static void __init pSeries_setup_arch(void)
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