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Subject[PATCH v2 03/17] arm64: Add per-cpu infrastructure to call ARCH_WORKAROUND_2
Date
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@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/kernel/cpu_errata.c | 2 ++
arch/arm64/kernel/entry.S | 11 +++++++----
2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index d98d8ce29533..d1a7a68dc142 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -233,6 +233,8 @@ enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
#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)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f33e6aed3037..29ad672a6abd 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -140,8 +140,10 @@ 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
@@ -176,12 +178,13 @@ alternative_cb_end
ldr x19, [tsk, #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
@@ -323,8 +326,8 @@ 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
--
2.14.2
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