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powerpc/64s: support nospectre_v2 cmdline option

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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>
This commit is contained in:
Christopher M. Riedl 2019-05-23 21:46:48 -05:00 • committed by Greg Kroah-Hartman
parent 4e23e97241
commit 1efaf619f4
1 changed files with 16 additions and 3 deletions
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19
arch/powerpc/kernel/security.c
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@ -29,7 +29,7 @@ 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
@ -107,7 +107,7 @@ 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;
@ -115,6 +115,9 @@ 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)
@ -390,7 +393,17 @@ 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