commit 986372c4367f46b34a3c0f6918d7fb95cbdf39d6 upstream.
In order to avoid checking arm64_ssbd_callback_required on each kernel entry/exit even if no mitigation is required, let's add yet another alternative that by default jumps over the mitigation, and that gets nop'ed out if we're doing dynamic mitigation.
Think of it as a poor man's static key...
Reviewed-by: Julien Grall julien.grall@arm.com Reviewed-by: Mark Rutland mark.rutland@arm.com Acked-by: Will Deacon will.deacon@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 --- arch/arm64/kernel/cpu_errata.c | 14 ++++++++++++++ arch/arm64/kernel/entry.S | 3 +++ 2 files changed, 17 insertions(+)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index b3df8e5986e0..012dab9d9a01 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -285,6 +285,20 @@ void __init arm64_update_smccc_conduit(struct alt_instr *alt, *updptr = cpu_to_le32(insn); }
+void __init arm64_enable_wa2_handling(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, + int nr_inst) +{ + BUG_ON(nr_inst != 1); + /* + * Only allow mitigation on EL1 entry/exit and guest + * ARCH_WORKAROUND_2 handling if the SSBD state allows it to + * be flipped. + */ + if (arm64_get_ssbd_state() == ARM64_SSBD_KERNEL) + *updptr = cpu_to_le32(aarch64_insn_gen_nop()); +} + static void arm64_set_ssbd_mitigation(bool state) { switch (psci_ops.conduit) { diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index caa77d060af1..5a585976d14c 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -142,6 +142,9 @@ alternative_else_nop_endif // to save/restore them if required. .macro apply_ssbd, state, targ, tmp1, tmp2 #ifdef CONFIG_ARM64_SSBD +alternative_cb arm64_enable_wa2_handling + b \targ +alternative_cb_end ldr_this_cpu \tmp2, arm64_ssbd_callback_required, \tmp1 cbz \tmp2, \targ mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2