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=... or nohz_full=... kernel parameters), 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@redhat.com>
---
 crypto/pcrypt.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
index 9d10b846ccf73..0162629a03957 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 +176,15 @@ 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;
+	const cpumask_t *hk_wq = housekeeping_cpumask(HK_TYPE_WQ);
 
 	cpu_index = (unsigned int)atomic_inc_return(&ictx->tfm_count) %
-		    cpumask_weight(cpu_online_mask);
+		    cpumask_weight_and(hk_wq, cpu_online_mask);
 
-	ctx->cb_cpu = cpumask_first(cpu_online_mask);
+	ctx->cb_cpu = cpumask_first_and(hk_wq, cpu_online_mask);
 	for (cpu = 0; cpu < cpu_index; cpu++)
-		ctx->cb_cpu = cpumask_next(ctx->cb_cpu, cpu_online_mask);
+		ctx->cb_cpu = cpumask_next_and(ctx->cb_cpu, hk_wq,
+					       cpu_online_mask);
 
 	cipher = crypto_spawn_aead(&ictx->spawn);
 
-- 
2.38.0

Friendly ping
(for this single patch)

On Thu, Oct 13, 2022 at 3:41 PM Leonardo Bras <leobras@redhat.com> 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=... or nohz_full=... kernel parameters), 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@redhat.com>
> ---
>  crypto/pcrypt.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
> index 9d10b846ccf73..0162629a03957 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 +176,15 @@ 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;
> +       const cpumask_t *hk_wq = housekeeping_cpumask(HK_TYPE_WQ);
>
>         cpu_index = (unsigned int)atomic_inc_return(&ictx->tfm_count) %
> -                   cpumask_weight(cpu_online_mask);
> +                   cpumask_weight_and(hk_wq, cpu_online_mask);
>
> -       ctx->cb_cpu = cpumask_first(cpu_online_mask);
> +       ctx->cb_cpu = cpumask_first_and(hk_wq, cpu_online_mask);
>         for (cpu = 0; cpu < cpu_index; cpu++)
> -               ctx->cb_cpu = cpumask_next(ctx->cb_cpu, cpu_online_mask);
> +               ctx->cb_cpu = cpumask_next_and(ctx->cb_cpu, hk_wq,
> +                                              cpu_online_mask);
>
>         cipher = crypto_spawn_aead(&ictx->spawn);
>
> --
> 2.38.0
>