[irqchip: irq/irqchip-next] irqchip/gic-v3-its: Flag device allocation as proxied if behind a PCI bridge

[irqchip-bot for Marc Zyngier]

The following commit has been merged into the irq/irqchip-next branch of irqchip:

Commit-ID:     34dd263fce3114147f21698f8e55e05b9e8185bd
Gitweb:        https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms/34dd263fce3114147f21698f8e55e05b9e8185bd
Author:        Marc Zyngier <maz@xxxxxxxxxx>
AuthorDate:    Sun, 29 Nov 2020 13:52:08 
Committer:     Marc Zyngier <maz@xxxxxxxxxx>
CommitterDate: Fri, 11 Dec 2020 14:47:50 

irqchip/gic-v3-its: Flag device allocation as proxied if behind a PCI bridge

An aliasing PCI bridge is another case where we should flag the
corresponding allocation as "proxied", as MSIs are coming with
the bridge's RID, and not the originating device's.

Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Tested-by: John Garry <john.garry@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20201129135208.680293-4-maz@xxxxxxxxxx
---
 drivers/irqchip/irq-gic-v3-its-pci-msi.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its-pci-msi.c b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
index 87711e0..ad2810c 100644
--- a/drivers/irqchip/irq-gic-v3-its-pci-msi.c
+++ b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
@@ -67,11 +67,16 @@ static int its_pci_msi_prepare(struct irq_domain *domain, struct device *dev,
 	/*
 	 * If pdev is downstream of any aliasing bridges, take an upper
 	 * bound of how many other vectors could map to the same DevID.
+	 * Also tell the ITS that the signalling will come from a proxy
+	 * device, and that special allocation rules apply.
 	 */
 	pci_for_each_dma_alias(pdev, its_get_pci_alias, &alias_dev);
-	if (alias_dev != pdev && alias_dev->subordinate)
-		pci_walk_bus(alias_dev->subordinate, its_pci_msi_vec_count,
-			     &alias_count);
+	if (alias_dev != pdev) {
+		if (alias_dev->subordinate)
+			pci_walk_bus(alias_dev->subordinate,
+				     its_pci_msi_vec_count, &alias_count);
+		info->flags |= MSI_ALLOC_FLAGS_PROXY_DEVICE;
+	}
 
 	/* ITS specific DeviceID, as the core ITS ignores dev. */
 	info->scratchpad[0].ul = pci_msi_domain_get_msi_rid(domain, pdev);