lkml.org 
[lkml]   [2022]   [Aug]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually
On Fri, Aug 05, 2022 at 05:21:14PM +0800, Liu Song wrote:
> From: Liu Song <liusong@linux.alibaba.com>
>
> In our environment, it was found that the mitigation BHB has a great
> impact on the benchmark performance. For example, in the lmbench test,
> the "process fork && exit" test performance drops by 20%.
> So it is necessary to have the ability to turn off the mitigation
> individually through cmdline, thus avoiding having to compile the
> kernel by adjusting the config.
>
> Signed-off-by: Liu Song <liusong@linux.alibaba.com>
> ---
> arch/arm64/kernel/proton-pack.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
> index 40be3a7..bd16903 100644
> --- a/arch/arm64/kernel/proton-pack.c
> +++ b/arch/arm64/kernel/proton-pack.c
> @@ -988,6 +988,14 @@ static void this_cpu_set_vectors(enum arm64_bp_harden_el1_vectors slot)
> isb();
> }
>
> +static bool __read_mostly __nospectre_bhb;
> +static int __init parse_spectre_bhb_param(char *str)
> +{
> + __nospectre_bhb = true;
> + return 0;
> +}
> +early_param("nospectre_bhb", parse_spectre_bhb_param);
> +
> void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
> {
> bp_hardening_cb_t cpu_cb;
> @@ -1001,7 +1009,7 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
> /* No point mitigating Spectre-BHB alone. */
> } else if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY)) {
> pr_info_once("spectre-bhb mitigation disabled by compile time option\n");
> - } else if (cpu_mitigations_off()) {
> + } else if (cpu_mitigations_off() || __nospectre_bhb) {
> pr_info_once("spectre-bhb mitigation disabled by command line option\n");
> } else if (supports_ecbhb(SCOPE_LOCAL_CPU)) {
> state = SPECTRE_MITIGATED;

It would be good to have an Ack (or a shrug) from somebody @arm.com on this
one.

Other than that, the documentation needs updating for the new option.

Will

\
 
 \ /
  Last update: 2022-08-26 12:41    [W:0.053 / U:0.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site