[RFC PATCH 3/6] vfio: Extend iommu-info to return MSIs automap state

[Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx>]

This patch allows the user-space to know whether msi-pages
are automatically mapped with some magic iova or not.

Even if the msi-pages are automatically mapped, still user-space
wants to over-ride the automatic iova selection for msi-mapping.
For this user-space need to know whether it is allowed to change
the automatic mapping or not and this API provides this mechanism.
Follow up patches will provide how to over-ride this.

Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 32 ++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h       |  3 +++
 2 files changed, 35 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index fa5d3e4..3315fb6 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -59,6 +59,7 @@ struct vfio_iommu {
 	struct rb_root		dma_list;
 	bool			v2;
 	bool			nesting;
+	bool			allow_msi_reconfig;
 	struct list_head	reserved_iova_list;
 };
 
@@ -1117,6 +1118,23 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
 	return ret;
 }
 
+static
+int vfio_domains_get_msi_maps(struct vfio_iommu *iommu,
+			      struct iommu_domain_msi_maps *msi_maps)
+{
+	struct vfio_domain *d;
+	int ret;
+
+	mutex_lock(&iommu->lock);
+	/* All domains have same msi-automap property, pick first */
+	d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
+	ret = iommu_domain_get_attr(d->domain, DOMAIN_ATTR_MSI_MAPPING,
+				    msi_maps);
+	mutex_unlock(&iommu->lock);
+
+	return ret;
+}
+
 static long vfio_iommu_type1_ioctl(void *iommu_data,
 				   unsigned int cmd, unsigned long arg)
 {
@@ -1138,6 +1156,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		}
 	} else if (cmd == VFIO_IOMMU_GET_INFO) {
 		struct vfio_iommu_type1_info info;
+		struct iommu_domain_msi_maps msi_maps;
+		int ret;
 
 		minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
 
@@ -1149,6 +1169,18 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 		info.flags = 0;
 
+		ret = vfio_domains_get_msi_maps(iommu, &msi_maps);
+		if (ret)
+			return ret;
+
+		if (msi_maps.override_automap) {
+			info.flags |= VFIO_IOMMU_INFO_MSI_ALLOW_RECONFIG;
+			iommu->allow_msi_reconfig = true;
+		}
+
+		if (msi_maps.automap)
+			info.flags |= VFIO_IOMMU_INFO_MSI_AUTOMAP;
+
 		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
 
 		return copy_to_user((void __user *)arg, &info, minsz);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 1abd1a9..9998f6e 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -391,6 +391,9 @@ struct vfio_iommu_type1_info {
 	__u32	argsz;
 	__u32	flags;
 #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
+#define VFIO_IOMMU_INFO_MSI_AUTOMAP (1 << 1)	/* MSI pages are auto-mapped
+						   in iommu */
+#define VFIO_IOMMU_INFO_MSI_ALLOW_RECONFIG (1 << 2) /* Allows reconfig automap*/
 	__u64	iova_pgsizes;		/* Bitmap of supported page sizes */
 };
 
-- 
1.9.3

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