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: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20221111122015.574339988@linutronix.de

diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
index edd0cc204e060424643b0d66f22e4d9851e0be1c..666ed21f292404417fde0ae975bb17ac7e72136b 100644 (file)
--- a/drivers/pci/msi/irqdomain.c
+++ b/drivers/pci/msi/irqdomain.c
@@ -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

diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
index 794ec97c5b7053246fb6d4ca1666a1aad7a87721..bc84647c6dbd466f5941b7bf86548bf69f3dca9c 100644 (file)
--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -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.

diff --git a/drivers/pci/msi/msi.h b/drivers/pci/msi/msi.h
index 8170ef2c5ad050757a1938307ca92fc49efa3d7c..9d75b6fb3e0c0742fd3231feebb9b06114679438 100644 (file)
--- a/drivers/pci/msi/msi.h
+++ b/drivers/pci/msi/msi.h
@@ -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