* [PATCH v4] powerpc/64s: support nospectre_v2 cmdline option
@ 2019-05-17 13:14 Christopher M. Riedl
0 siblings, 0 replies; only message in thread
From: Christopher M. Riedl @ 2019-05-17 13:14 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Christopher M. Riedl, Andrew Donnellan
Add support for disabling the kernel implemented spectre v2 mitigation
(count cache flush on context switch) via the nospectre_v2 and
mitigations=off cmdline options.
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Christopher M. Riedl <cmr@informatik.wtf>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
---
v3->v4:
add support for new mitigations=off cmdline option
arch/powerpc/kernel/security.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index e1c9cf079503..88ae6a9bdf74 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
@@ -114,7 +114,7 @@ static __init int security_feature_debugfs_init(void)
device_initcall(security_feature_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;
@@ -122,6 +122,9 @@ 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 || cpu_mitigations_off())
@@ -399,7 +402,17 @@ static void toggle_count_cache_flush(bool enable)
void setup_count_cache_flush(void)
{
- toggle_count_cache_flush(true);
+ bool enable = true;
+
+ if (no_spectrev2 || cpu_mitigations_off()) {
+ 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");
+
+ enable = false;
+ }
+
+ toggle_count_cache_flush(enable);
}
#ifdef CONFIG_DEBUG_FS
--
2.21.0
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