Re: [PATCH 07/14] arm64: ssbd: Skip apply_ssbd if not using dynamic mitigation
On Tue, May 22, 2018 at 04:06:41PM +0100, Marc Zyngier wrote:
> 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...
I guess in future we can magic up a more general asm static key if we
need them elsewhere.
> Signed-off-by: Marc Zyngier
Reviewed-by: Mark Rutland
Mark.
> ---
> 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 f1d4e75b0ddd..8f686f39b9c1 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -283,6 +283,20 @@ 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_EL1_ENTRY)
> + *updptr = cpu_to_le32(aarch64_insn_gen_nop());
> +}
> +
> static void do_ssbd(bool state)
> {
> switch (psci_ops.conduit) {
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 29ad672a6abd..e6f6e2339b22 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
> --
> 2.14.2
>
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Re: [PATCH 07/14] arm64: ssbd: Skip apply_ssbd if not using dynamic mitigation
Hi Marc,
On 05/22/2018 04:06 PM, Marc Zyngier wrote:
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...
Signed-off-by: Marc Zyngier
Reviewed-by: Julien Grall
Cheers,
---
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 f1d4e75b0ddd..8f686f39b9c1 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -283,6 +283,20 @@ 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_EL1_ENTRY)
+ *updptr = cpu_to_le32(aarch64_insn_gen_nop());
+}
+
static void do_ssbd(bool state)
{
switch (psci_ops.conduit) {
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 29ad672a6abd..e6f6e2339b22 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
--
Julien Grall
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[PATCH 07/14] arm64: ssbd: Skip apply_ssbd if not using dynamic mitigation
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...
Signed-off-by: Marc Zyngier
---
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 f1d4e75b0ddd..8f686f39b9c1 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -283,6 +283,20 @@ 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_EL1_ENTRY)
+ *updptr = cpu_to_le32(aarch64_insn_gen_nop());
+}
+
static void do_ssbd(bool state)
{
switch (psci_ops.conduit) {
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 29ad672a6abd..e6f6e2339b22 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
--
2.14.2
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