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Commit 19d98b4d authored by Christopher M. Riedl's avatar Christopher M. Riedl Committed by Greg Kroah-Hartman
Browse files

powerpc/64s: support nospectre_v2 cmdline option 



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: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarChristopher M. Riedl <cmr@informatik.wtf>
Reviewed-by: default avatarAndrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190524024647.381-1-cmr@informatik.wtf


Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b7e2a040

arch/powerpc/kernel/security.c

+16 −3
Original line number Diff line number Diff line
@@ -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 || cpu_mitigations_off())
@@ -391,7 +394,17 @@ 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