Commit d2a463b2 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

PCI/MSI: Reject multi-MSI early 



When hierarchical MSI interrupt domains are enabled then there is no point
to do tons of work and detect the missing support for multi-MSI late in the
allocation path.

Just query the domain feature flags right away. The query function is going
to be used for other purposes later and has a mode argument which influences
the result:

  ALLOW_LEGACY returns true when:
     - there is no irq domain attached (legacy support)
     - there is a irq domain attached which has the feature flag set

  DENY_LEGACY returns only true when:
     - there is a irq domain attached which has the feature flag set

This allows to use the function universally without ifdeffery in the
calling code.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20221111122015.574339988@linutronix.de
parent bab65e48

drivers/pci/msi/irqdomain.c

+22 −0
Original line number Diff line number Diff line
@@ -187,6 +187,28 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode, 
}

EXPORT_SYMBOL_GPL(pci_msi_create_irq_domain);



/**

 * pci_msi_domain_supports - Check for support of a particular feature flag

 * @pdev:		The PCI device to operate on

 * @feature_mask:	The feature mask to check for (full match)

 * @mode:		If ALLOW_LEGACY this grants the feature when there is no irq domain

 *			associated to the device. If DENY_LEGACY the lack of an irq domain

 *			makes the feature unsupported

 */

bool pci_msi_domain_supports(struct pci_dev *pdev, unsigned int feature_mask,

			     enum support_mode mode)

{

	struct msi_domain_info *info;

	struct irq_domain *domain;



	domain = dev_get_msi_domain(&pdev->dev);



	if (!domain || !irq_domain_is_hierarchy(domain))

		return mode == ALLOW_LEGACY;

	info = domain->host_data;

	return (info->flags & feature_mask) == feature_mask;

}



/*

 * Users of the generic MSI infrastructure expect a device to have a single ID,

 * so with DMA aliases we have to pick the least-worst compromise. Devices with

drivers/pci/msi/msi.c

+4 −0
Original line number Diff line number Diff line
@@ -347,6 +347,10 @@ static int msi_capability_init(struct pci_dev *dev, int nvec, 
	struct msi_desc *entry;

	int ret;



	/* Reject multi-MSI early on irq domain enabled architectures */

	if (nvec > 1 && !pci_msi_domain_supports(dev, MSI_FLAG_MULTI_PCI_MSI, ALLOW_LEGACY))

		return 1;



	/*

	 * Disable MSI during setup in the hardware, but mark it enabled

	 * so that setup code can evaluate it.

drivers/pci/msi/msi.h

+9 −0
Original line number Diff line number Diff line
@@ -97,6 +97,15 @@ int __pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries, int 
void __pci_restore_msi_state(struct pci_dev *dev);

void __pci_restore_msix_state(struct pci_dev *dev);



/* irq_domain related functionality */



enum support_mode {

	ALLOW_LEGACY,

	DENY_LEGACY,

};



bool pci_msi_domain_supports(struct pci_dev *dev, unsigned int feature_mask, enum support_mode mode);



/* Legacy (!IRQDOMAIN) fallbacks */



#ifdef CONFIG_PCI_MSI_ARCH_FALLBACKS