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SubjectRe: [PATCH 03/14] arm64: Add per-cpu infrastructure to call ARCH_WORKAROUND_2
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Hi Marc,

On 05/22/2018 04:06 PM, Marc Zyngier wrote:
> In a heterogeneous system, we can end up with both affected and
> unaffected CPUs. Let's check their status before calling into the
> firmware.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Reviewed-by: Julien Grall <julien.grall@arm.com>

Cheers,

> ---
> 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 46b3aafb631a..0288d6cf560e 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
>

--
Julien Grall

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