linux-kernel - [PATCH 5.13 232/351] PCI: iproc: Support multi-MSI only on uniprocessor kernel

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Date:   Mon, 19 Jul 2021 16:52:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
        Sandor Bodo-Merle <sbodomerle@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Pali Rohár <pali@...nel.org>,
        Ray Jui <ray.jui@...adcom.com>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.13 232/351] PCI: iproc: Support multi-MSI only on uniprocessor kernel

From: Sandor Bodo-Merle <sbodomerle@...il.com>

[ 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@gmail.com
Fixes: fc54bae28818 ("PCI: iproc: Allow allocation of multiple MSIs")
Reported-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Sandor Bodo-Merle <sbodomerle@...il.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Acked-by: Marc Zyngier <maz@...nel.org>
Acked-by: Pali Rohár <pali@...nel.org>
Acked-by: Ray Jui <ray.jui@...adcom.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/pci/controller/pcie-iproc-msi.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-iproc-msi.c b/drivers/pci/controller/pcie-iproc-msi.c
index 557d93dcb3bc..81b4effeb130 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);
 
 	/*
@@ -540,6 +543,9 @@ 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");
-- 
2.30.2