From: "Christopher M. Riedl" cmr@informatik.wtf
commit d8f0e0b073e1ec52a05f0c2a56318b47387d2f10 upstream.
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 Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20190524024647.381-1-cmr@informatik.wtf Signed-off-by: Daniel Axtens dja@axtens.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/security.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)
--- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c @@ -29,7 +29,7 @@ static enum count_cache_flush_type count 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
@@ -107,7 +107,7 @@ static __init int barrier_nospec_debugfs 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; @@ -115,6 +115,9 @@ static int __init handle_nospectre_v2(ch 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) @@ -390,7 +393,17 @@ static void toggle_count_cache_flush(boo
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