arm64: Add workaround for Arm Cortex-A77 erratum 1508412
On Cortex-A77 r0p0 and r1p0, a sequence of a non-cacheable or device load
and a store exclusive or PAR_EL1 read can cause a deadlock.
The workaround requires a DMB SY before and after a PAR_EL1 register
read. In addition, it's possible an interrupt (doing a device read) or
KVM guest exit could be taken between the DMB and PAR read, so we
also need a DMB before returning from interrupt and before returning to
a guest.
A deadlock is still possible with the workaround as KVM guests must also
have the workaround. IOW, a malicious guest can deadlock an affected
systems.
This workaround also depends on a firmware counterpart to enable the h/w
to insert DMB SY after load and store exclusive instructions. See the
errata document SDEN-1152370 v10 [1] for more information.
[1] https://static.docs.arm.com/101992/0010/Arm_Cortex_A77_MP074_Software_Developer_Errata_Notice_v10.pdf
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: kvmarm@lists.cs.columbia.edu
Link: https://lore.kernel.org/r/20201028182839.166037-2-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 24d75af..61314fd 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -523,6 +523,16 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
.cpu_enable = cpu_enable_trap_ctr_access,
},
#endif
+#ifdef CONFIG_ARM64_ERRATUM_1508412
+ {
+ /* we depend on the firmware portion for correctness */
+ .desc = "ARM erratum 1508412 (kernel portion)",
+ .capability = ARM64_WORKAROUND_1508412,
+ ERRATA_MIDR_RANGE(MIDR_CORTEX_A77,
+ 0, 0,
+ 1, 0),
+ },
+#endif
{
}
};
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f30007d..b295fb9 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -365,6 +365,9 @@
br x30
#endif
.else
+ /* Ensure any device/NC reads complete */
+ alternative_insn nop, "dmb sy", ARM64_WORKAROUND_1508412
+
eret
.endif
sb
