PCI/MSI: Size device MSI domain with the maximum number of vectors

JIRA: https://issues.redhat.com/browse/RHEL-120705
Upstream Status: 9cc82d9

commit 9cc82d9
Author: Marc Zyngier <maz@kernel.org>
Date:   Tue Jun 3 15:18:01 2025 +0100

    PCI/MSI: Size device MSI domain with the maximum number of vectors

    Zenghui reports that since 1396e89 ("genirq/msi: Move prepare() call
    to per-device allocation"), his Multi-MSI capable device isn't working
    anymore.

    This is a consequence of 15c72f8 ("PCI/MSI: Add support for per device
    MSI[X] domains"), which always creates a MSI domain of size 1, even in the
    presence of Multi-MSI.

    While this was somehow working until then, moving the .prepare() call ends
    up sizing the ITS table with a tiny value for this device, and making the
    endpoint driver unhappy.

    Instead, always create the domain and call the .prepare() helper with the
    maximum expected size.

    Fixes: 1396e89 ("genirq/msi: Move prepare() call to per-device allocation")
    Fixes: 15c72f8 ("PCI/MSI: Add support for per device MSI[X] domains")
    Reported-by: Zenghui Yu <yuzenghui@huawei.com>
    Signed-off-by: Marc Zyngier <maz@kernel.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Zenghui Yu <yuzenghui@huawei.com>
    Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
    Link: https://lore.kernel.org/all/20250603141801.915305-1-maz@kernel.org
    Closes: https://lore.kernel.org/r/0b1d7aec-1eac-a9cd-502a-339e216e08a1@huawei.com

Signed-off-by: Myron Stowe <mstowe@redhat.com>

Author: Myron Stowe

drivers/pci/msi/irqdomain.c

@@ -309,6 +309,7 @@ static bool pci_create_device_domain(struct pci_dev *pdev, const struct msi_doma
 /**
  * pci_setup_msi_device_domain - Setup a device MSI interrupt domain
  * @pdev:	The PCI device to create the domain on
+ * @hwsize:	The maximum number of MSI vectors
  *
  * Return:
  *  True when:
@@ -325,7 +326,7 @@ static bool pci_create_device_domain(struct pci_dev *pdev, const struct msi_doma
  *	- The device is removed
  *	- MSI is disabled and a MSI-X domain is created
  */
-bool pci_setup_msi_device_domain(struct pci_dev *pdev)
+bool pci_setup_msi_device_domain(struct pci_dev *pdev, unsigned int hwsize)
 {
 	if (WARN_ON_ONCE(pdev->msix_enabled))
 		return false;
@@ -335,7 +336,7 @@ bool pci_setup_msi_device_domain(struct pci_dev *pdev)
 	if (pci_match_device_domain(pdev, DOMAIN_BUS_PCI_DEVICE_MSIX))
 		msi_remove_device_irq_domain(&pdev->dev, MSI_DEFAULT_DOMAIN);
 
-	return pci_create_device_domain(pdev, &pci_msi_template, 1);
+	return pci_create_device_domain(pdev, &pci_msi_template, hwsize);
 }
 
 /**

drivers/pci/msi/msi.c

@@ -439,16 +439,16 @@ int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
 	if (nvec < minvec)
 		return -ENOSPC;
 
-	if (nvec > maxvec)
-		nvec = maxvec;
-
 	rc = pci_setup_msi_context(dev);
 	if (rc)
 		return rc;
 
-	if (!pci_setup_msi_device_domain(dev))
+	if (!pci_setup_msi_device_domain(dev, nvec))
 		return -ENODEV;
 
+	if (nvec > maxvec)
+		nvec = maxvec;
+
 	for (;;) {
 		if (affd) {
 			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);

drivers/pci/msi/msi.h

@@ -107,7 +107,7 @@ enum support_mode {
 };
 
 bool pci_msi_domain_supports(struct pci_dev *dev, unsigned int feature_mask, enum support_mode mode);
-bool pci_setup_msi_device_domain(struct pci_dev *pdev);
+bool pci_setup_msi_device_domain(struct pci_dev *pdev, unsigned int hwsize);
 bool pci_setup_msix_device_domain(struct pci_dev *pdev, unsigned int hwsize);
 
 /* Legacy (!IRQDOMAIN) fallbacks */