Patch "PCI: iproc: Support multi-MSI only on uniprocessor kernel" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    PCI: iproc: Support multi-MSI only on uniprocessor kernel

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pci-iproc-support-multi-msi-only-on-uniprocessor-ker.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f16b909c53831aac50f75482e83bd328543b8854
Author: Sandor Bodo-Merle <sbodomerle@xxxxxxxxx>
Date:   Tue Jun 22 17:26:30 2021 +0200

    PCI: iproc: Support multi-MSI only on uniprocessor kernel
    
    [ Upstream commit 2dc0a201d0f59e6818ef443609f0850a32910844 ]
    
    The interrupt affinity scheme used by this driver is incompatible with
    multi-MSI as it implies moving the doorbell address to that of another MSI
    group.  This isn't possible for multi-MSI, as all the MSIs must have the
    same doorbell address. As such it is restricted to systems with a single
    CPU.
    
    Link: https://lore.kernel.org/r/20210622152630.40842-2-sbodomerle@xxxxxxxxx
    Fixes: fc54bae28818 ("PCI: iproc: Allow allocation of multiple MSIs")
    Reported-by: Marc Zyngier <maz@xxxxxxxxxx>
    Signed-off-by: Sandor Bodo-Merle <sbodomerle@xxxxxxxxx>
    Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
    Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
    Acked-by: Pali Rohár <pali@xxxxxxxxxx>
    Acked-by: Ray Jui <ray.jui@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/pci/controller/pcie-iproc-msi.c b/drivers/pci/controller/pcie-iproc-msi.c
index b77811dcead1..0cb2fa1e0af4 100644
--- a/drivers/pci/controller/pcie-iproc-msi.c
+++ b/drivers/pci/controller/pcie-iproc-msi.c
@@ -171,7 +171,7 @@ static struct irq_chip iproc_msi_irq_chip = {
 
 static struct msi_domain_info iproc_msi_domain_info = {
 	.flags = MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
-		MSI_FLAG_MULTI_PCI_MSI | MSI_FLAG_PCI_MSIX,
+		MSI_FLAG_PCI_MSIX,
 	.chip = &iproc_msi_irq_chip,
 };
 
@@ -250,6 +250,9 @@ static int iproc_msi_irq_domain_alloc(struct irq_domain *domain,
 	struct iproc_msi *msi = domain->host_data;
 	int hwirq, i;
 
+	if (msi->nr_cpus > 1 && nr_irqs > 1)
+		return -EINVAL;
+
 	mutex_lock(&msi->bitmap_lock);
 
 	/*
@@ -539,6 +542,9 @@ int iproc_msi_init(struct iproc_pcie *pcie, struct device_node *node)
 	mutex_init(&msi->bitmap_lock);
 	msi->nr_cpus = num_possible_cpus();
 
+	if (msi->nr_cpus == 1)
+		iproc_msi_domain_info.flags |=  MSI_FLAG_MULTI_PCI_MSI;
+
 	msi->nr_irqs = of_irq_count(node);
 	if (!msi->nr_irqs) {
 		dev_err(pcie->dev, "found no MSI GIC interrupt\n");