| From foo@baz Fri Jul 20 11:55:21 CEST 2018 |
| From: Marc Zyngier <marc.zyngier@arm.com> |
| Date: Fri, 20 Jul 2018 10:47:15 +0100 |
| Subject: arm64: ssbd: Skip apply_ssbd if not using dynamic mitigation |
| To: stable@vger.kernel.org |
| Cc: Will Deacon <will.deacon@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Mark Rutland <mark.rutland@arm.com>, Christoffer Dall <christoffer.dall@arm.com> |
| Message-ID: <20180720094722.702-8-marc.zyngier@arm.com> |
| |
| From: Marc Zyngier <marc.zyngier@arm.com> |
| |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/arm64/kernel/cpu_errata.c | 14 ++++++++++++++ |
| arch/arm64/kernel/entry.S | 3 +++ |
| 2 files changed, 17 insertions(+) |
| |
| --- a/arch/arm64/kernel/cpu_errata.c |
| +++ b/arch/arm64/kernel/cpu_errata.c |
| @@ -289,6 +289,20 @@ void __init arm64_update_smccc_conduit(s |
| *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) { |
| --- 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 |
