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Commit 42f967de authored by Marc Zyngier's avatar Marc Zyngier Committed by Greg Kroah-Hartman
Browse files

arm64: ssbd: Skip apply_ssbd if not using dynamic mitigation 



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: default avatarJulien Grall <julien.grall@arm.com>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 242bff38

arch/arm64/kernel/cpu_errata.c

+14 −0
Original line number Diff line number Diff line
@@ -244,6 +244,20 @@ 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) {

arch/arm64/kernel/entry.S

+3 −0
Original line number Diff line number Diff line
@@ -100,6 +100,9 @@ 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