linux-kernel - [PATCH v1 1/4] iommu: Define iommu_get/put_msi_cookie() under CONFIG_IRQ_MSI

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Message-ID: <b5ec70595b63017598a256db71af8feff28c6733.1740600272.git.nicolinc@nvidia.com>
Date: Wed, 26 Feb 2025 12:16:04 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: <robin.murphy@....com>, <joro@...tes.org>, <will@...nel.org>,
	<alex.williamson@...hat.com>
CC: <jgg@...dia.com>, <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>
Subject: [PATCH v1 1/4] iommu: Define iommu_get/put_msi_cookie() under CONFIG_IRQ_MSI_IOMMU

Not all domain owners call iommu_get_dma/msi_cookie(), e.g. iommufd has
its sw_msi implementation without using the domain->iova_cookie but the
domain->iommufd_hwpt.

To isolate the unused iova_cookie from the iommufd, iommu_domain_free()
will no longer call iommu_put_dma_cookie().

Add iommu_put_msi_cookie() to pair with iommu_put_dma_cookie() for VFIO
that is the only caller to explicitly put the MSI cookie.

Move iommufd_get/put_msi_cookie() inside "ifdef CONFIG_IRQ_MSI_IOMMU".

Note that the iommufd_get_msi_cookie now returns a 0 for NOP in case of:
 *) !CONFIG_IOMMU_DMA - the caller in VFIO would have returned prior to
                        reaching to this function.
 *) !CONFIG_IRQ_MSI_IOMMU - in a system without an irqchip driver, vfio
                            or iommufd shouldn't fail if an IOMMU driver
                            still reports SW_MSI reserved regions.

Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 include/linux/iommu.h     | 10 +++++++---
 drivers/iommu/dma-iommu.c | 12 ++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e93d2e918599..6f66980e0c86 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1534,12 +1534,16 @@ void iommu_debugfs_setup(void);
 static inline void iommu_debugfs_setup(void) {}
 #endif
 
-#ifdef CONFIG_IOMMU_DMA
+#if defined(CONFIG_IOMMU_DMA) && IS_ENABLED(CONFIG_IRQ_MSI_IOMMU)
 int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);
-#else /* CONFIG_IOMMU_DMA */
+void iommu_put_msi_cookie(struct iommu_domain *domain);
+#else /* CONFIG_IOMMU_DMA && CONFIG_IRQ_MSI_IOMMU */
 static inline int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
 {
-	return -ENODEV;
+	return 0;
+}
+static inline void iommu_put_msi_cookie(struct iommu_domain *domain)
+{
 }
 #endif	/* CONFIG_IOMMU_DMA */
 
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 94263ed2c564..228524c81b72 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -418,6 +418,7 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
  * number of PAGE_SIZE mappings necessary to cover every MSI doorbell address
  * used by the devices attached to @domain.
  */
+#if IS_ENABLED(CONFIG_IRQ_MSI_IOMMU)
 int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
 {
 	struct iommu_dma_cookie *cookie;
@@ -439,6 +440,17 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
 }
 EXPORT_SYMBOL(iommu_get_msi_cookie);
 
+/**
+ * iommu_put_msi_cookie - Release a domain's MSI remapping resources
+ * @domain: IOMMU domain previously prepared by iommu_get_msi_cookie()
+ */
+void iommu_put_msi_cookie(struct iommu_domain *domain)
+{
+	iommu_put_dma_cookie(domain);
+}
+EXPORT_SYMBOL_GPL(iommu_put_msi_cookie);
+#endif
+
 /**
  * iommu_put_dma_cookie - Release a domain's DMA mapping resources
  * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie() or
-- 
2.43.0