linux-kernel - Re: [PATCH v1 1/1] crypto/pcrypt: Do not use isolated CPUs for callback

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Date:   Wed, 5 Oct 2022 09:57:49 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Leonardo Bras <leobras@...hat.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] crypto/pcrypt: Do not use isolated CPUs for
 callback

On Tue, Oct 04, 2022 at 03:25:37AM -0300, Leonardo Bras wrote:
> Currently pcrypt_aead_init_tfm() will pick callback cpus (ctx->cb_cpu)
> from any online cpus. Later padata_reorder() will queue_work_on() the
> chosen cb_cpu.
> 
> This is undesired if the chosen cb_cpu is listed as isolated (i.e. using
> isolcpus=... kernel parameter), since the work queued will interfere with
> the workload on the isolated cpu.
> 
> Make sure isolated cpus are not used for pcrypt.
> 
> Signed-off-by: Leonardo Bras <leobras@...hat.com>
> ---
>  crypto/pcrypt.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
> index 9d10b846ccf73..9017d08c91a8d 100644
> --- a/crypto/pcrypt.c
> +++ b/crypto/pcrypt.c
> @@ -16,6 +16,7 @@
>  #include <linux/kobject.h>
>  #include <linux/cpu.h>
>  #include <crypto/pcrypt.h>
> +#include <linux/sched/isolation.h>
>  
>  static struct padata_instance *pencrypt;
>  static struct padata_instance *pdecrypt;
> @@ -175,13 +176,16 @@ static int pcrypt_aead_init_tfm(struct crypto_aead *tfm)
>  	struct pcrypt_instance_ctx *ictx = aead_instance_ctx(inst);
>  	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(tfm);
>  	struct crypto_aead *cipher;
> +	struct cpumask non_isolated;
> +
> +	cpumask_and(&non_isolated, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN));

Since certain systems do not use isolcpus=domain, so please use a flag
that is setup by nohz_full=, for example HK_FLAG_MISC:

static int __init housekeeping_nohz_full_setup(char *str)
{
        unsigned long flags;

        flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
                HK_FLAG_MISC | HK_FLAG_KTHREAD;

        return housekeeping_setup(str, flags);
}
__setup("nohz_full=", housekeeping_nohz_full_setup);

Also, shouldnt you use cpumask_t ?

Looks good otherwise.

Thanks!


>  
>  	cpu_index = (unsigned int)atomic_inc_return(&ictx->tfm_count) %
> -		    cpumask_weight(cpu_online_mask);
> +		    cpumask_weight(&non_isolated);
>  
> -	ctx->cb_cpu = cpumask_first(cpu_online_mask);
> +	ctx->cb_cpu = cpumask_first(&non_isolated);
>  	for (cpu = 0; cpu < cpu_index; cpu++)
> -		ctx->cb_cpu = cpumask_next(ctx->cb_cpu, cpu_online_mask);
> +		ctx->cb_cpu = cpumask_next(ctx->cb_cpu, &non_isolated);
>  
>  	cipher = crypto_spawn_aead(&ictx->spawn);
>  
> -- 
> 2.37.3
> 
>