From a242ee827f46802b0cb9249a35f36f4807d525f5 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Tue, 29 May 2018 13:11:12 +0100
Subject: [PATCH 10/12] arm64: ssbd: Restore mitigation status on CPU resume

Git-commit: 647d0519b53f440a55df163de21c52a8205431cc
Patch-mainline: v4.18-rc1
References: bsc#1085308

On a system where firmware can dynamically change the state of the
mitigation, the CPU will always come up with the mitigation enabled,
including when coming back from suspend.

If the user has requested "no mitigation" via a command line option,
let's enforce it by calling into the firmware again to disable it.

Similarily, for a resume from hibernate, the mitigation could have
been disabled by the boot kernel. Let's ensure that it is set
back on in that case.

Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 arch/arm64/include/asm/cpufeature.h |  6 ++++++
 arch/arm64/kernel/cpu_errata.c      |  2 +-
 arch/arm64/kernel/hibernate.c       | 11 +++++++++++
 arch/arm64/kernel/suspend.c         |  8 ++++++++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index a2415ee6b8a3..c5bc80a03515 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -278,6 +278,12 @@ static inline int arm64_get_ssbd_state(void)
 #endif
 }
 
+#ifdef CONFIG_ARM64_SSBD
+void arm64_set_ssbd_mitigation(bool state);
+#else
+static inline void arm64_set_ssbd_mitigation(bool state) {}
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 0f18d03561bf..702e002737b7 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -285,7 +285,7 @@ void __init arm64_enable_wa2_handling(struct alt_instr *alt,
 		*updptr = cpu_to_le32(aarch64_insn_gen_nop());
 }
 
-static void arm64_set_ssbd_mitigation(bool state)
+void arm64_set_ssbd_mitigation(bool state)
 {
 	switch (psci_ops.conduit) {
 	case PSCI_CONDUIT_HVC:
diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index f20cf7e99249..a3a3c6039f89 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -313,6 +313,17 @@ int swsusp_arch_suspend(void)
 
 		sleep_cpu = -EINVAL;
 		__cpu_suspend_exit();
+
+		/*
+		 * Just in case the boot kernel did turn the SSBD
+		 * mitigation off behind our back, let's set the state
+		 * to what we expect it to be.
+		 */
+		switch (arm64_get_ssbd_state()) {
+		case ARM64_SSBD_FORCE_ENABLE:
+		case ARM64_SSBD_KERNEL:
+			arm64_set_ssbd_mitigation(true);
+		}
 	}
 
 	local_daif_restore(flags);
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index d2d2edac78f2..0b6f903892c0 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -62,6 +62,14 @@ void notrace __cpu_suspend_exit(void)
 	 */
 	if (hw_breakpoint_restore)
 		hw_breakpoint_restore(cpu);
+
+	/*
+	 * On resume, firmware implementing dynamic mitigation will
+	 * have turned the mitigation on. If the user has forcefully
+	 * disabled it, make sure their wishes are obeyed.
+	 */
+	if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE)
+		arm64_set_ssbd_mitigation(false);
 }
 
 /*
-- 
2.11.0