Add support for disabling the kernel implemented spectre v2 mitigation
(count cache flush on context switch) via the nospectre_v2 cmdline
option.
Suggested-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Christopher M. Riedl <c...@informatik.wtf>
---
v1->v2:
add call to toggle_count_cache_flush(false)
arch/powerpc/kernel/security.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index b33bafb8fcea..d775da9b9227 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -28,7 +28,7 @@ static enum count_cache_flush_type count_cache_flush_type =
COUNT_CACHE_FLUSH_NO
bool barrier_nospec_enabled;
static bool no_nospec;
static bool btb_flush_enabled;
-#ifdef CONFIG_PPC_FSL_BOOK3E
+#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
static bool no_spectrev2;
#endif
@@ -106,7 +106,7 @@ static __init int barrier_nospec_debugfs_init(void)
device_initcall(barrier_nospec_debugfs_init);
#endif /* CONFIG_DEBUG_FS */
-#ifdef CONFIG_PPC_FSL_BOOK3E
+#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
static int __init handle_nospectre_v2(char *p)
{
no_spectrev2 = true;
@@ -114,6 +114,9 @@ static int __init handle_nospectre_v2(char *p)
return 0;
}
early_param("nospectre_v2", handle_nospectre_v2);
+#endif /* CONFIG_PPC_FSL_BOOK3E || CONFIG_PPC_BOOK3S_64 */
+
+#ifdef CONFIG_PPC_FSL_BOOK3E
void setup_spectre_v2(void)
{
if (no_spectrev2)
@@ -391,6 +394,15 @@ static void toggle_count_cache_flush(bool enable)
void setup_count_cache_flush(void)
{
+ if (no_spectrev2) {
+ if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED)
+ || security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED))
+ pr_warn("Spectre v2 mitigations not under software
control, can't disable\n");
+
+ toggle_count_cache_flush(false);
+ return;
+ }
+
toggle_count_cache_flush(true);
}
--
2.21.0
