linux-kernel - [patch 09/10] PCI/MSI: Provide pci_msix_expand_vectors[

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Date:   Sat, 27 Nov 2021 02:25:11 +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 09/10] PCI/MSI: Provide pci_msix_expand_vectors[_at]()

Provide a new interface which allows to expand the MSI-X vector space if
the underlying irq domain implementation supports it.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 drivers/pci/msi/msi.c |   41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h   |   13 +++++++++++++
 2 files changed, 54 insertions(+)

--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -1025,6 +1025,47 @@ int pci_alloc_irq_vectors_affinity(struc
 EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);
 
 /**
+ * pci_msix_expand_vectors_at - Expand MSI-X interrupts for a device
+ *
+ * @dev:	PCI device to operate on
+ * @at:		Allocate at MSI-X index. If @at == PCI_MSI_EXPAND_AUTO
+ *		the function expands automatically after the last
+ *		active index.
+ * @nvec:	Number of vectors to allocate
+ *
+ * Expand the MSI-X vectors of a device after an initial enablement and
+ * allocation.
+ *
+ * Return: 0 if the allocation was successful, an error code otherwise.
+ */
+int pci_msix_expand_vectors_at(struct pci_dev *dev, unsigned int at, unsigned int nvec)
+{
+	struct msi_device_data *md = dev->dev.msi.data;
+	struct msi_range range = { .ndesc = nvec, };
+	unsigned int max_vecs;
+	int ret;
+
+	if (!pci_msi_enable || !dev || !dev->msix_enabled || !md)
+		return -ENOTSUPP;
+
+	if (!pci_msi_domain_supports_expand(dev))
+		return -ENOTSUPP;
+
+	max_vecs = pci_msix_vec_count(dev);
+	if (!nvec || nvec > max_vecs)
+		return -EINVAL;
+
+	range.first = at == PCI_MSIX_EXPAND_AUTO ? md->num_descs : at;
+
+	if (range.first >= max_vecs || nvec > max_vecs - range.first)
+		return -ENOSPC;
+
+	ret = msix_setup_interrupts(dev, dev->msix_base, &range, NULL, NULL, true);
+	return ret <= 0 ? ret : -ENOSPC;;
+}
+EXPORT_SYMBOL_GPL(pci_msix_expand_vectors_at);
+
+/**
  * pci_free_irq_vectors - free previously allocated IRQs for a device
  * @dev:		PCI device to operate on
  *
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1534,6 +1534,7 @@ static inline int pci_enable_msix_exact(
 int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 				   unsigned int max_vecs, unsigned int flags,
 				   struct irq_affinity *affd);
+int pci_msix_expand_vectors_at(struct pci_dev *dev, unsigned int at, unsigned int nvec);
 
 void pci_free_irq_vectors(struct pci_dev *dev);
 int pci_irq_vector(struct pci_dev *dev, unsigned int nr);
@@ -1565,6 +1566,11 @@ pci_alloc_irq_vectors_affinity(struct pc
 	return -ENOSPC;
 }
 
+static inline int pci_msix_expand_vectors_at(struct pci_dev *dev, unsigned int at, unsigned int nvec)
+{
+	return -ENOTSUPP;
+}
+
 static inline void pci_free_irq_vectors(struct pci_dev *dev)
 {
 }
@@ -1582,6 +1588,13 @@ static inline const struct cpumask *pci_
 }
 #endif
 
+#define PCI_MSIX_EXPAND_AUTO	(UINT_MAX)
+
+static inline int pci_msix_expand_vectors(struct pci_dev *dev, unsigned int nvec)
+{
+	return pci_msix_expand_vectors_at(dev, PCI_MSIX_EXPAND_AUTO, nvec);
+}
+
 /**
  * pci_irqd_intx_xlate() - Translate PCI INTx value to an IRQ domain hwirq
  * @d: the INTx IRQ domain