Re: [PATCH v6 2/4] s390/pci: Reuse FMB buffer and preserve state in device re-enablement

[Matthew Rosato <mjrosato@linux.ibm.com>]

> +int zpci_fmb_reenable_device(struct zpci_dev *zdev)
> +{
> +	u64 req = ZPCI_CREATE_REQ(zdev->fh, 0, ZPCI_MOD_FC_SET_MEASURE);
> +	struct zpci_fib fib = {0};
> +	u8 cc, status;
> +
> +	lockdep_assert_held(&zdev->fmb_lock);
> +
> +	if (!zdev->fmb_enabled)
> +		return zpci_fmb_enable_device(zdev);

Sashiko has a point here, won't all paths that call zpci_reenable_device
now unconditionally turn on FMB here even if it was purposely disabled?

The pattern of callers for zpci_reenable_device() is:

zpci_disable_device()
...
zpci_reenable_device()

We only care to re-enable the FMB during device re-enable if the device
had FMB enabled at the time zpci_disable_device() was called.

Thanks,
Matt

> +
> +	fib.gd = zdev->gisa;
> +	cc = zpci_mod_fc(req, &fib, &status); /* Disable function measurement */
> +
> +	/* Unlike in zpci_fmb_disable_device(), cc == 3 is not a valid state here
> +	 * because we are re-enabling function measurement for the same function
> +	 * handle.
> +	 */
> +	if (cc)
> +		return -EIO;
> +
> +	zdev->fmb_enabled = 0;
> +	return zpci_fmb_enable_device(zdev);
> +}
> +EXPORT_SYMBOL_GPL(zpci_fmb_reenable_device);