[PATCH 3.10 120/129] arm64: virt: ensure visibility of __boot_cpu_mode

From: Greg Kroah-Hartman
Date: Mon Jan 06 2014 - 17:42:04 EST

3.10-stable review patch. If anyone has any objections, please let me know.


From: Mark Rutland <mark.rutland@xxxxxxx>

commit 82b2f495fba338d1e3098dde1df54944a9c19751 upstream.

Secondary CPUs write to __boot_cpu_mode with caches disabled, and thus a
cached value of __boot_cpu_mode may be incoherent with that in memory.
This could lead to a failure to detect mismatched boot modes.

This patch adds flushing to ensure that writes by secondaries to
__boot_cpu_mode are made visible before we test against it.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <cdall@xxxxxxxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/arm64/include/asm/virt.h | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -21,6 +21,7 @@
#define BOOT_CPU_MODE_EL2 (0x0e12b007)

#ifndef __ASSEMBLY__
+#include <asm/cacheflush.h>

* __boot_cpu_mode records what mode CPUs were booted in.
@@ -36,9 +37,20 @@ extern u32 __boot_cpu_mode[2];
void __hyp_set_vectors(phys_addr_t phys_vector_base);
phys_addr_t __hyp_get_vectors(void);

+static inline void sync_boot_mode(void)
+ /*
+ * As secondaries write to __boot_cpu_mode with caches disabled, we
+ * must flush the corresponding cache entries to ensure the visibility
+ * of their writes.
+ */
+ __flush_dcache_area(__boot_cpu_mode, sizeof(__boot_cpu_mode));
/* Reports the availability of HYP mode */
static inline bool is_hyp_mode_available(void)
+ sync_boot_mode();
return (__boot_cpu_mode[0] == BOOT_CPU_MODE_EL2 &&
__boot_cpu_mode[1] == BOOT_CPU_MODE_EL2);
@@ -46,6 +58,7 @@ static inline bool is_hyp_mode_available
/* Check if the bootloader has booted CPUs in different modes */
static inline bool is_hyp_mode_mismatched(void)
+ sync_boot_mode();
return __boot_cpu_mode[0] != __boot_cpu_mode[1];

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