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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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