linux-kernel - [patch 08/10] PCI/MSI: Provide pci_msi_domain_supports

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Date:   Sat, 27 Nov 2021 02:24:42 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Cooper <amc96@....ac.uk>,
        Juergen Gross <jgross@...e.com>, linux-pci@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: [patch 08/10] PCI/MSI: Provide pci_msi_domain_supports_expand()

Not all irq domain implementations can support runtime MSI-X vector
expansion as they assume zero based allocations or have other
restrictions.

The legacy PCI allocation functions are not suited for runtime vector
expansion either.

Add a function which allows to query whether runtime MSI-X vector expansion
is supported or not.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 drivers/pci/msi/irqdomain.c |   29 +++++++++++++++++++++++------
 include/linux/msi.h         |    2 ++
 2 files changed, 25 insertions(+), 6 deletions(-)

--- a/drivers/pci/msi/irqdomain.c
+++ b/drivers/pci/msi/irqdomain.c
@@ -8,12 +8,18 @@
 
 #include "msi.h"
 
+static struct irq_domain *pci_get_msi_domain(struct pci_dev *dev)
+{
+	struct irq_domain *domain = dev_get_msi_domain(&dev->dev);
+
+	return domain && irq_domain_is_hierarchy(domain) ? domain : NULL;
+}
+
 int pci_msi_setup_msi_irqs(struct pci_dev *dev, struct msi_range *range, int type)
 {
-	struct irq_domain *domain;
+	struct irq_domain *domain = pci_get_msi_domain(dev);
 
-	domain = dev_get_msi_domain(&dev->dev);
-	if (domain && irq_domain_is_hierarchy(domain))
+	if (domain)
 		return msi_domain_alloc_irqs_descs_locked(domain, &dev->dev, range);
 
 	return pci_msi_legacy_setup_msi_irqs(dev, range->ndesc, type);
@@ -21,15 +27,26 @@ int pci_msi_setup_msi_irqs(struct pci_de
 
 void pci_msi_teardown_msi_irqs(struct pci_dev *dev, struct msi_range *range)
 {
-	struct irq_domain *domain;
+	struct irq_domain *domain = pci_get_msi_domain(dev);
 
-	domain = dev_get_msi_domain(&dev->dev);
-	if (domain && irq_domain_is_hierarchy(domain))
+	if (domain)
 		msi_domain_free_irqs_descs_locked(domain, &dev->dev, range);
 	else
 		pci_msi_legacy_teardown_msi_irqs(dev);
 }
 
+bool pci_msi_domain_supports_expand(struct pci_dev *dev)
+{
+	struct irq_domain *domain = pci_get_msi_domain(dev);
+	struct msi_domain_info *info;
+
+	if (!domain)
+		return false;
+
+	info = domain->host_data;
+	return info->flags & MSI_FLAG_CAN_EXPAND;
+}
+
 /**
  * pci_msi_domain_write_msg - Helper to write MSI message to PCI config space
  * @irq_data:	Pointer to interrupt data of the MSI interrupt
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -552,11 +552,13 @@ struct irq_domain *pci_msi_create_irq_do
 u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
 struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
 bool pci_dev_has_special_msi_domain(struct pci_dev *pdev);
+bool pci_msi_domain_supports_expand(struct pci_dev *dev);
 #else
 static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
 {
 	return NULL;
 }
+static inline bool pci_msi_domain_supports_expand(struct pci_dev *dev) { return false; }
 #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
 
 #endif /* LINUX_MSI_H */