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Subject[tip: irq/core] PCI/MSI: Reject multi-MSI early
The following commit has been merged into the irq/core branch of tip:

Commit-ID: d2a463b297415ca6dd4d60bb1c867dd7c931587b
Gitweb: https://git.kernel.org/tip/d2a463b297415ca6dd4d60bb1c867dd7c931587b
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Fri, 11 Nov 2022 14:55:09 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 17 Nov 2022 15:15:22 +01:00

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

---
drivers/pci/msi/irqdomain.c | 22 ++++++++++++++++++++++
drivers/pci/msi/msi.c | 4 ++++
drivers/pci/msi/msi.h | 9 +++++++++
3 files changed, 35 insertions(+)

diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
index edd0cc2..666ed21 100644
--- 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 794ec97..bc84647 100644
--- 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 8170ef2..9d75b6f 100644
--- 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
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