[PATCH 4.9 54/66] arm64: Add per-cpu infrastructure to call ARCH_WORKAROUND_2

From: Greg Kroah-Hartman
Date: Fri Jul 20 2018 - 08:31:20 EST


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

------------------

From: Marc Zyngier <marc.zyngier@xxxxxxx>

commit 5cf9ce6e5ea50f805c6188c04ed0daaec7b6887d upstream.

In a heterogeneous system, we can end up with both affected and
unaffected CPUs. Let's check their status before calling into the
firmware.

Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/cpu_errata.c | 2 ++
arch/arm64/kernel/entry.S | 11 +++++++----
2 files changed, 9 insertions(+), 4 deletions(-)

--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -188,6 +188,8 @@ static int enable_smccc_arch_workaround_
#endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */

#ifdef CONFIG_ARM64_SSBD
+DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
+
void __init arm64_update_smccc_conduit(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr,
int nr_inst)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -98,8 +98,10 @@ alternative_else_nop_endif

// This macro corrupts x0-x3. It is the caller's duty
// to save/restore them if required.
- .macro apply_ssbd, state
+ .macro apply_ssbd, state, targ, tmp1, tmp2
#ifdef CONFIG_ARM64_SSBD
+ ldr_this_cpu \tmp2, arm64_ssbd_callback_required, \tmp1
+ cbz \tmp2, \targ
mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2
mov w1, #\state
alternative_cb arm64_update_smccc_conduit
@@ -135,12 +137,13 @@ alternative_cb_end
ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug
disable_step_tsk x19, x20 // exceptions when scheduling.

- apply_ssbd 1
+ apply_ssbd 1, 1f, x22, x23

#ifdef CONFIG_ARM64_SSBD
ldp x0, x1, [sp, #16 * 0]
ldp x2, x3, [sp, #16 * 1]
#endif
+1:

mov x29, xzr // fp pointed to user-space
.else
@@ -210,8 +213,8 @@ alternative_if ARM64_WORKAROUND_845719
alternative_else_nop_endif
#endif
3:
- apply_ssbd 0
-
+ apply_ssbd 0, 5f, x0, x1
+5:
.endif
msr elr_el1, x21 // set up the return data
msr spsr_el1, x22