Hi,
On 11/19/20 7:36 AM, Jerry Snitselaar wrote:
>
> Matthew Garrett @ 2020-10-15 15:39 MST:
>
>> On Thu, Oct 15, 2020 at 2:44 PM Jerry Snitselaar <jsnitsel@xxxxxxxxxx> wrote:
>>>
>>> There is a misconfiguration in the bios of the gpio pin used for the
>>> interrupt in the T490s. When interrupts are enabled in the tpm_tis
>>> driver code this results in an interrupt storm. This was initially
>>> reported when we attempted to enable the interrupt code in the tpm_tis
>>> driver, which previously wasn't setting a flag to enable it. Due to
>>> the reports of the interrupt storm that code was reverted and we went back
>>> to polling instead of using interrupts. Now that we know the T490s problem
>>> is a firmware issue, add code to check if the system is a T490s and
>>> disable interrupts if that is the case. This will allow us to enable
>>> interrupts for everyone else. If the user has a fixed bios they can
>>> force the enabling of interrupts with tpm_tis.interrupts=1 on the
>>> kernel command line.
>>
>> I think an implication of this is that systems haven't been
>> well-tested with interrupts enabled. In general when we've found a
>> firmware issue in one place it ends up happening elsewhere as well, so
>> it wouldn't surprise me if there are other machines that will also be
>> unhappy with interrupts enabled. Would it be possible to automatically
>> detect this case (eg, if we get more than a certain number of
>> interrupts in a certain timeframe immediately after enabling the
>> interrupt) and automatically fall back to polling in that case? It
>> would also mean that users with fixed firmware wouldn't need to pass a
>> parameter.
>
> I believe Matthew is correct here. I found another system today
> with completely different vendor for both the system and the tpm chip.
> In addition another Lenovo model, the L490, has the issue.
>
> This initial attempt at a solution like Matthew suggested works on
> the system I found today, but I imagine it is all sorts of wrong.
> In the 2 systems where I've seen it, there are about 100000 interrupts
> in around 1.5 seconds, and then the irq code shuts down the interrupt
> because they aren't being handled.
Is that with your patch? The IRQ should be silenced as soon as
devm_free_irq(chip->dev.parent, priv->irq, chip); is called.
Depending on if we can get your storm-detection to work or not,
we might also choose to just never try to use the IRQ (at least on
x86 systems). AFAIK the TPM is never used for high-throughput stuff
so the polling overhead should not be a big deal (and I'm getting the feeling
that Windows always polls).
Regards,
Hans
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 49ae09ac604f..478e9d02a3fa 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -27,6 +27,11 @@
> #include "tpm.h"
> #include "tpm_tis_core.h"
>
> +static unsigned int time_start = 0;
> +static bool storm_check = true;
> +static bool storm_killed = false;
> +static u32 irqs_fired = 0;
> +
> static void tpm_tis_clkrun_enable(struct tpm_chip *chip, bool value);
>
> static void tpm_tis_enable_interrupt(struct tpm_chip *chip, u8 mask)
> @@ -464,25 +469,31 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
> return rc;
> }
>
> -static void disable_interrupts(struct tpm_chip *chip)
> +static void __disable_interrupts(struct tpm_chip *chip)
> {
> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> u32 intmask;
> int rc;
>
> - if (priv->irq == 0)
> - return;
> -
> rc = tpm_tis_read32(priv, TPM_INT_ENABLE(priv->locality), &intmask);
> if (rc < 0)
> intmask = 0;
>
> intmask &= ~TPM_GLOBAL_INT_ENABLE;
> rc = tpm_tis_write32(priv, TPM_INT_ENABLE(priv->locality), intmask);
> + chip->flags &= ~TPM_CHIP_FLAG_IRQ;
> +}
> +
> +static void disable_interrupts(struct tpm_chip *chip)
> +{
> + struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>
> + if (priv->irq == 0)
> + return;
> +
> + __disable_interrupts(chip);
> devm_free_irq(chip->dev.parent, priv->irq, chip);
> priv->irq = 0;
> - chip->flags &= ~TPM_CHIP_FLAG_IRQ;
> }
>
> /*
> @@ -528,6 +539,12 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
> int rc, irq;
> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>
> + if (unlikely(storm_killed)) {
> + devm_free_irq(chip->dev.parent, priv->irq, chip);
> + priv->irq = 0;
> + storm_killed = false;
> + }
> +
> if (!(chip->flags & TPM_CHIP_FLAG_IRQ) || priv->irq_tested)
> return tpm_tis_send_main(chip, buf, len);
>
> @@ -748,6 +765,21 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
> u32 interrupt;
> int i, rc;
>
> + if (storm_check) {
> + irqs_fired++;
> +
> + if (!time_start) {
> + time_start = jiffies_to_msecs(jiffies);
> + } else if ((irqs_fired > 1000) && (jiffies_to_msecs(jiffies) - jiffies < 500)) {
> + __disable_interrupts(chip);
> + storm_check = false;
> + storm_killed = true;
> + return IRQ_HANDLED;
> + } else if ((jiffies_to_msecs(jiffies) - time_start > 500) && (irqs_fired < 1000)) {
> + storm_check = false;
> + }
> + }
> +
> rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &interrupt);
> if (rc < 0)
> return IRQ_NONE;
>
