Re: [patch V4 02/21] irqchip: Provide irq-msi-lib

[Lorenzo Pieralisi <lpieralisi@kernel.org>]

On Sun, Jun 23, 2024 at 05:18:34PM +0200, Thomas Gleixner wrote:

[...]

> diff --git a/drivers/irqchip/irq-msi-lib.c b/drivers/irqchip/irq-msi-lib.c
> new file mode 100644
> index 000000000000..acbccf8f7f5b
> --- /dev/null
> +++ b/drivers/irqchip/irq-msi-lib.c
> @@ -0,0 +1,112 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (C) 2022 Linutronix GmbH
> +// Copyright (C) 2022 Intel
> +
> +#include <linux/export.h>
> +
> +#include "irq-msi-lib.h"
> +
> +/**
> + * msi_lib_init_dev_msi_info - Domain info setup for MSI domains
> + * @dev:		The device for which the domain is created for
> + * @domain:		The domain providing this callback
> + * @real_parent:	The real parent domain of the domain to be initialized
> + *			which might be a domain built on top of @domain or
> + *			@domain itself
> + * @info:		The domain info for the domain to be initialize
> + *
> + * This function is to be used for all types of MSI domains above the root
> + * parent domain and any intermediates. The topmost parent domain specific
> + * functionality is determined via @real_parent.
> + *
> + * All intermediate domains between the root and the device domain must
> + * have either msi_parent_ops.init_dev_msi_info = msi_parent_init_dev_msi_info
> + * or invoke it down the line.
> + */
> +bool msi_lib_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
> +			       struct irq_domain *real_parent,
> +			       struct msi_domain_info *info)
> +{
> +	const struct msi_parent_ops *pops = real_parent->msi_parent_ops;
> +
> +	/*
> +	 * MSI parent domain specific settings. For now there is only the
> +	 * root parent domain, e.g. NEXUS, acting as a MSI parent, but it is
> +	 * possible to stack MSI parents. See x86 vector -> irq remapping
> +	 */
> +	if (domain->bus_token == pops->bus_select_token) {
> +		if (WARN_ON_ONCE(domain != real_parent))
> +			return false;
> +	} else {
> +		WARN_ON_ONCE(1);
> +		return false;
> +	}
> +
> +	/* Parent ops available? */
> +	if (WARN_ON_ONCE(!pops))

We have already dereferenced pops above, we should move this warning
before we dereference it (ie checked devmsi-arm-v4-2 too - branch same
comment applies there too).

Thanks
Lorenzo

> +		return false;
> +
> +	/* Is the target domain bus token supported? */
> +	switch(info->bus_token) {
> +	default:
> +		/*
> +		 * This should never be reached. See
> +		 * msi_lib_irq_domain_select()
> +		 */
> +		WARN_ON_ONCE(1);
> +		return false;
> +	}
> +
> +	/*
> +	 * Mask out the domain specific MSI feature flags which are not
> +	 * supported by the real parent.
> +	 */
> +	info->flags			&= pops->supported_flags;
> +	/* Enforce the required flags */
> +	info->flags			|= pops->required_flags;
> +
> +	/* Chip updates for all child bus types */
> +	if (!info->chip->irq_eoi)
> +		info->chip->irq_eoi	= irq_chip_eoi_parent;
> +
> +	/*
> +	 * The device MSI domain can never have a set affinity callback. It
> +	 * always has to rely on the parent domain to handle affinity
> +	 * settings. The device MSI domain just has to write the resulting
> +	 * MSI message into the hardware which is the whole purpose of the
> +	 * device MSI domain aside of mask/unmask which is provided e.g. by
> +	 * PCI/MSI device domains.
> +	 */
> +	info->chip->irq_set_affinity	= msi_domain_set_affinity;
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(msi_lib_init_dev_msi_info);
> +
> +/**
> + * msi_lib_irq_domain_select - Shared select function for NEXUS domains
> + * @d:		Pointer to the irq domain on which select is invoked
> + * @fwspec:	Firmware spec describing what is searched
> + * @bus_token:	The bus token for which a matching irq domain is looked up
> + *
> + * Returns:	%0 if @d is not what is being looked for
> + *
> + *		%1 if @d is either the domain which is directly searched for or
> + *		   if @d is providing the parent MSI domain for the functionality
> + *			 requested with @bus_token.
> + */
> +int msi_lib_irq_domain_select(struct irq_domain *d, struct irq_fwspec *fwspec,
> +			      enum irq_domain_bus_token bus_token)
> +{
> +	const struct msi_parent_ops *ops = d->msi_parent_ops;
> +	u32 busmask = BIT(bus_token);
> +
> +	if (fwspec->fwnode != d->fwnode || fwspec->param_count != 0)
> +		return 0;
> +
> +	/* Handle pure domain searches */
> +	if (bus_token == ops->bus_select_token)
> +		return 1;
> +
> +	return ops && !!(ops->bus_select_mask & busmask);
> +}
> +EXPORT_SYMBOL_GPL(msi_lib_irq_domain_select);
> diff --git a/drivers/irqchip/irq-msi-lib.h b/drivers/irqchip/irq-msi-lib.h
> new file mode 100644
> index 000000000000..f0706cc28264
> --- /dev/null
> +++ b/drivers/irqchip/irq-msi-lib.h
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (C) 2022 Linutronix GmbH
> +// Copyright (C) 2022 Intel
> +
> +#ifndef _DRIVERS_IRQCHIP_IRQ_MSI_LIB_H
> +#define _DRIVERS_IRQCHIP_IRQ_MSI_LIB_H
> +
> +#include <linux/bits.h>
> +#include <linux/irqdomain.h>
> +#include <linux/msi.h>
> +
> +int msi_lib_irq_domain_select(struct irq_domain *d, struct irq_fwspec *fwspec,
> +			      enum irq_domain_bus_token bus_token);
> +
> +bool msi_lib_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
> +			       struct irq_domain *real_parent,
> +			       struct msi_domain_info *info);
> +
> +#endif /* _DRIVERS_IRQCHIP_IRQ_MSI_LIB_H */
> -- 
> 2.34.1
> 
>