arm64: ssbd: Restore mitigation status on CPU resume

commit 647d0519b53f440a55df163de21c52a8205431cc upstream.

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: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index a2415ee6b8a306d819eca143532c3b3a9ed2fc09..c5bc80a035152c8c1dd2ecc0bb5302ec2dbb320e 100644 (file)
--- 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 012dab9d9a010c64ac7051038a4b3841ce632aaa..eccdb28b4a39c98c3d55686bd7647a7e3732acc3 100644 (file)
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -299,7 +299,7 @@ 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 095d3c170f5d2e44eb1f849009ef3b658bb2c667..a028cc95afe17383485877553657d2f21b230043 100644 (file)
--- 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_dbg_restore(flags);

diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 77cd655e6eb72bb72f284172f2cbb0685309fd81..7a655e60cf4b3f342dcedd7e8a425a08e89c2072 100644 (file)
--- 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);
 }
 
 /*