[RFC v3 5/8] vfio/type1: Report 1st-level/stage-1 page table format to userspace

["Liu, Yi L" <yi.l.liu@intel.com>]

From: Liu Yi L <yi.l.liu@intel.com>

VFIO exposes IOMMU nesting translation (a.k.a dual stage translation)
capability to userspace. Thus applications like QEMU could support
vIOMMU with hardware's nesting translation capability for pass-through
devices. Before setting up nesting translation for pass-through devices,
QEMU and other applications need to learn the supported 1st-lvl/stage-1
translation structure format like page table format.

Take vSVA (virtual Shared Virtual Addressing) as an example, to support
vSVA for pass-through devices, QEMU setup nesting translation for pass-
through devices. The guest page table are configured to host as 1st-lvl/
stage-1 page table. Therefore, guest format should be compatible with
host side.

This patch reports the supported 1st-lvl/stage-1 page table format on the
current platform to userspace. QEMU and other alike applications should
use this format info when trying to setup IOMMU nesting translation on
host IOMMU.

Cc: Kevin Tian <kevin.tian@intel.com>
CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
---
 drivers/vfio/vfio_iommu_type1.c | 79 +++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h       |  7 ++++
 2 files changed, 86 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 1cf75f5..e0bbcfb 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2243,6 +2243,81 @@ static int vfio_iommu_type1_pasid_free(struct vfio_iommu *iommu,
 	return ret;
 }
 
+static int vfio_iommu_get_pasid_format(struct vfio_iommu *iommu,
+					u32 *pasid_format)
+{
+	struct vfio_domain *domain;
+	u32 format = 0, tmp_format = 0;
+	int ret;
+
+	mutex_lock(&iommu->lock);
+	if (list_empty(&iommu->domain_list)) {
+		mutex_unlock(&iommu->lock);
+		return -EINVAL;
+	}
+
+	list_for_each_entry(domain, &iommu->domain_list, next) {
+		if (iommu_domain_get_attr(domain->domain,
+			DOMAIN_ATTR_PASID_FORMAT, &format)) {
+			ret = -EINVAL;
+			format = 0;
+			goto out_unlock;
+		}
+		/*
+		 * format is always non-zero (the first format is
+		 * IOMMU_PASID_FORMAT_INTEL_VTD which is 1). For
+		 * the reason of potential different backed IOMMU
+		 * formats, here we expect to have identical formats
+		 * in the domain list, no miexed formats support.
+		 * return -EINVAL to fail the attempt of setup
+		 * VFIO_TYPE1_NESTING_IOMMU if non-identical formats
+		 * are detected.
+		 */
+		if (tmp_format && tmp_format != format) {
+			ret = -EINVAL;
+			format = 0;
+			goto out_unlock;
+		}
+
+		tmp_format = format;
+	}
+	ret = 0;
+
+out_unlock:
+	if (format)
+		*pasid_format = format;
+	mutex_unlock(&iommu->lock);
+	return ret;
+}
+
+static int vfio_iommu_info_add_nesting_cap(struct vfio_iommu *iommu,
+					 struct vfio_info_cap *caps)
+{
+	struct vfio_info_cap_header *header;
+	struct vfio_iommu_type1_info_cap_nesting *nesting_cap;
+	u32 format = 0;
+	int ret;
+
+	ret = vfio_iommu_get_pasid_format(iommu, &format);
+	if (ret) {
+		pr_warn("Failed to get domain format\n");
+		return ret;
+	}
+
+	header = vfio_info_cap_add(caps, sizeof(*nesting_cap) + sizeof(format),
+				   VFIO_IOMMU_TYPE1_INFO_CAP_NESTING, 1);
+	if (IS_ERR(header))
+		return PTR_ERR(header);
+
+	nesting_cap = container_of(header,
+				struct vfio_iommu_type1_info_cap_nesting,
+				header);
+
+	nesting_cap->pasid_format = format;
+
+	return 0;
+}
+
 static int vfio_iommu_type1_set_pasid_quota(struct vfio_iommu *iommu,
 					    u32 quota)
 {
@@ -2313,6 +2388,10 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		if (ret)
 			return ret;
 
+		ret = vfio_iommu_info_add_nesting_cap(iommu, &caps);
+		if (ret)
+			return ret;
+
 		if (caps.size) {
 			info.flags |= VFIO_IOMMU_INFO_CAPS;
 
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 62113be..633c07f 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -748,6 +748,13 @@ struct vfio_iommu_type1_info_cap_iova_range {
 	struct	vfio_iova_range iova_ranges[];
 };
 
+#define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING  2
+
+struct vfio_iommu_type1_info_cap_nesting {
+	struct	vfio_info_cap_header header;
+	__u32	pasid_format;
+};
+
 #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
 
 /**
-- 
2.7.4