linux-kernel - Re: [PATCH v2] tpm_tis: Disable interrupts if interrupt storm detected

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Date:   Mon, 30 Nov 2020 20:26:06 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Peter Huewe <peterhuewe@....de>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Hans de Goede <hdegoede@...hat.com>
Subject: Re: [PATCH v2] tpm_tis: Disable interrupts if interrupt storm detected


Jerry Snitselaar @ 2020-11-30 19:58 MST:

> When enabling the interrupt code for the tpm_tis driver we have
> noticed some systems have a bios issue causing an interrupt storm to
> occur. The issue isn't limited to a single tpm or system manufacturer
> so keeping a denylist of systems with the issue isn't optimal. Instead
> try to detect the problem occurring, disable interrupts, and revert to
> polling when it happens.
>
> Cc: Jarkko Sakkinen <jarkko@...nel.org>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Peter Huewe <peterhuewe@....de>
> Cc: James Bottomley <James.Bottomley@...senPartnership.com>
> Cc: Matthew Garrett <mjg59@...gle.com>
> Cc: Hans de Goede <hdegoede@...hat.com>
> Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
> ---
> v2: drop tpm_tis specific workqueue and use just system_wq
>
> drivers/char/tpm/tpm_tis_core.c | 27 +++++++++++++++++++++++++++
>  drivers/char/tpm/tpm_tis_core.h |  2 ++
>  2 files changed, 29 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 23b60583928b..72cc8a5a152c 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -24,6 +24,8 @@
>  #include <linux/wait.h>
>  #include <linux/acpi.h>
>  #include <linux/freezer.h>
> +#include <linux/workqueue.h>
> +#include <linux/kernel_stat.h>
>  #include "tpm.h"
>  #include "tpm_tis_core.h"
>  
> @@ -745,9 +747,23 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
>  {
>  	struct tpm_chip *chip = dev_id;
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> +	static bool check_storm = true;
> +	static unsigned int check_start;
>  	u32 interrupt;
>  	int i, rc;
>  
> +	if (unlikely(check_storm)) {
> +		if (!check_start) {
> +			check_start = jiffies_to_msecs(jiffies);
> +		} else if ((kstat_irqs(priv->irq) > 1000) &&
> +			   (jiffies_to_msecs(jiffies) - check_start < 500)) {
> +			check_storm = false;
> +			schedule_work(&priv->storm_work);
> +		} else if (jiffies_to_msecs(jiffies) - check_start >= 500) {
> +			check_storm = false;
> +		}
> +	}
> +
>  	rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &interrupt);
>  	if (rc < 0)
>  		return IRQ_NONE;
> @@ -987,6 +1003,14 @@ static const struct tpm_class_ops tpm_tis = {
>  	.clk_enable = tpm_tis_clkrun_enable,
>  };
>  
> +static void tpm_tis_storm_work(struct work_struct *work)
> +{
> +	struct tpm_tis_data *priv = container_of(work, struct tpm_tis_data, storm_work);
> +
> +	disable_interrupts(priv->chip);
> +	dev_warn(&priv->chip->dev, "Interrupt storm detected, using polling.\n");
> +}
> +
>  int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  		      const struct tpm_tis_phy_ops *phy_ops,
>  		      acpi_handle acpi_dev_handle)
> @@ -1003,6 +1027,9 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  	if (IS_ERR(chip))
>  		return PTR_ERR(chip);
>  
> +	priv->chip = chip;
> +	INIT_WORK(&priv->storm_work, tpm_tis_storm_work);
> +
>  #ifdef CONFIG_ACPI
>  	chip->acpi_dev_handle = acpi_dev_handle;
>  #endif
> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> index edeb5dc61c95..5630f294dc0c 100644
> --- a/drivers/char/tpm/tpm_tis_core.h
> +++ b/drivers/char/tpm/tpm_tis_core.h
> @@ -95,6 +95,8 @@ struct tpm_tis_data {
>  	u16 clkrun_enabled;
>  	wait_queue_head_t int_queue;
>  	wait_queue_head_t read_queue;
> +	struct work_struct storm_work;
> +	struct tpm_chip *chip;
>  	const struct tpm_tis_phy_ops *phy_ops;
>  	unsigned short rng_quality;
>  };

I've tested this with the Intel platform that has an Infineon chip that
I found the other week. It works, but isn't the complete fix. With this
on top of James' patchset I sometimes see the message "Lost Interrupt
waiting for TPM stat", so I guess there needs to be a check in
wait_for_tpm_stat and request_locality to see if interrupts were
disabled when the wait_event_interruptible_timeout call times out.