linux-kernel - [RFC PATCH v2 01/18] genirq/msi: Provide DOMAIN_BUS_MSI

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Message-ID: <20250920203851.2205115-21-ajones@ventanamicro.com>
Date: Sat, 20 Sep 2025 15:38:51 -0500
From: Andrew Jones <ajones@...tanamicro.com>
To: iommu@...ts.linux.dev,
	kvm-riscv@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: jgg@...dia.com,
	zong.li@...ive.com,
	tjeznach@...osinc.com,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	anup@...infault.org,
	atish.patra@...ux.dev,
	tglx@...utronix.de,
	alex.williamson@...hat.com,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	alex@...ti.fr
Subject: [RFC PATCH v2 01/18] genirq/msi: Provide DOMAIN_BUS_MSI_REMAP

Provide a domain bus token for the upcoming support for the RISC-V
IOMMU interrupt remapping domain, which needs to be distinguished
from NEXUS domains. The new token name is generic, as the only
information that needs to be conveyed is that the IRQ domain will
remap MSIs, i.e. there's nothing RISC-V specific to convey.

Since the MSI_REMAP domain implements init_dev_msi_info() with
msi_parent_init_dev_msi_info(), which makes 'domain' point to
the NEXUS domain, while keeping 'msi_parent_domain' pointing to
itself, there's nothing to do in msi-lib to add support except
to accept the token.

Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
---
 drivers/irqchip/irq-msi-lib.c  | 8 ++++----
 include/linux/irqdomain_defs.h | 1 +
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/irq-msi-lib.c b/drivers/irqchip/irq-msi-lib.c
index 908944009c21..90ef0af866eb 100644
--- a/drivers/irqchip/irq-msi-lib.c
+++ b/drivers/irqchip/irq-msi-lib.c
@@ -36,14 +36,14 @@ bool msi_lib_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
 		return false;
 
 	/*
-	 * MSI parent domain specific settings. For now there is only the
-	 * root parent domain, e.g. NEXUS, acting as a MSI parent, but it is
-	 * possible to stack MSI parents. See x86 vector -> irq remapping
+	 * MSI parent domain specific settings. There may be only the root
+	 * parent domain, e.g. NEXUS, acting as a MSI parent, or there may
+	 * be stacked MSI parents, typically used for remapping.
 	 */
 	if (domain->bus_token == pops->bus_select_token) {
 		if (WARN_ON_ONCE(domain != real_parent))
 			return false;
-	} else {
+	} else if (real_parent->bus_token != DOMAIN_BUS_MSI_REMAP) {
 		WARN_ON_ONCE(1);
 		return false;
 	}
diff --git a/include/linux/irqdomain_defs.h b/include/linux/irqdomain_defs.h
index 36653e2ee1c9..676eca8147ae 100644
--- a/include/linux/irqdomain_defs.h
+++ b/include/linux/irqdomain_defs.h
@@ -27,6 +27,7 @@ enum irq_domain_bus_token {
 	DOMAIN_BUS_AMDVI,
 	DOMAIN_BUS_DEVICE_MSI,
 	DOMAIN_BUS_WIRED_TO_MSI,
+	DOMAIN_BUS_MSI_REMAP,
 };
 
 #endif /* _LINUX_IRQDOMAIN_DEFS_H */
-- 
2.49.0