[PATCH 4/4] vfio: vfio_iommu_type1: implement VFIO_IOMMU_INFO_CAPABILITIES

[Pierre Morel]

We implement a capability intercafe for VFIO_IOMMU_GET_INFO and add the
first capability: VFIO_IOMMU_INFO_CAPABILITIES.

When calling the ioctl, the user must specify
VFIO_IOMMU_INFO_CAPABILITIES to retrieve the capabilities and must check
in the answer if capabilities are supported.
Older kernel will not check nor set the VFIO_IOMMU_INFO_CAPABILITIES in
the flags of vfio_iommu_type1_info.

The iommu get_attr callback will be called to retrieve the specific
attributes and fill the capabilities, VFIO_IOMMU_INFO_CAP_QFN for the
PCI query function attributes and VFIO_IOMMU_INFO_CAP_QGRP for the
PCI query function group.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 95 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 94 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index d0f731c..f7f8120 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -1658,6 +1658,70 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
 	return ret;
 }
 
+int vfio_iommu_type1_caps(struct vfio_iommu *iommu, struct vfio_info_cap *caps,
+			  size_t size)
+{
+	struct vfio_domain *d;
+	struct vfio_iommu_type1_info_block *info_fn;
+	struct vfio_iommu_type1_info_block *info_grp;
+	unsigned long total_size, fn_size, grp_size;
+	int ret;
+
+	d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
+	if (!d)
+		return -ENODEV;
+	/* The size of these capabilities are device dependent */
+	fn_size = iommu_domain_get_attr(d->domain,
+					DOMAIN_ATTR_ZPCI_FN_SIZE, NULL);
+	if (fn_size < 0)
+		return fn_size;
+	fn_size +=  sizeof(struct vfio_info_cap_header);
+	total_size = fn_size;
+
+	grp_size = iommu_domain_get_attr(d->domain,
+					 DOMAIN_ATTR_ZPCI_GRP_SIZE, NULL);
+	if (grp_size < 0)
+		return grp_size;
+	grp_size +=  sizeof(struct vfio_info_cap_header);
+	total_size += grp_size;
+
+	/* Tell caller to call us with a greater buffer */
+	if (total_size > size) {
+		caps->size = total_size;
+		return 0;
+	}
+
+	info_fn = kzalloc(fn_size, GFP_KERNEL);
+	if (!info_fn)
+		return -ENOMEM;
+	ret = iommu_domain_get_attr(d->domain,
+				    DOMAIN_ATTR_ZPCI_FN, &info_fn->data);
+	if (ret < 0)
+		return ret;
+
+	info_fn->header.id = VFIO_IOMMU_INFO_CAP_QFN;
+
+	ret = vfio_info_add_capability(caps, &info_fn->header, fn_size);
+	if (ret)
+		goto err_fn;
+
+	info_grp = kzalloc(grp_size, GFP_KERNEL);
+	if (!info_grp)
+		goto err_fn;
+	ret = iommu_domain_get_attr(d->domain,
+				    DOMAIN_ATTR_ZPCI_GRP, &info_grp->data);
+	if (ret < 0)
+		goto err_grp;
+	info_grp->header.id = VFIO_IOMMU_INFO_CAP_QGRP;
+	ret = vfio_info_add_capability(caps, &info_grp->header, grp_size);
+
+err_grp:
+	kfree(info_grp);
+err_fn:
+	kfree(info_fn);
+	return ret;
+}
+
 static long vfio_iommu_type1_ioctl(void *iommu_data,
 				   unsigned int cmd, unsigned long arg)
 {
@@ -1679,6 +1743,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		}
 	} else if (cmd == VFIO_IOMMU_GET_INFO) {
 		struct vfio_iommu_type1_info info;
+		struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+		int ret;
 
 		minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
 
@@ -1688,7 +1754,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		if (info.argsz < minsz)
 			return -EINVAL;
 
-		info.flags = VFIO_IOMMU_INFO_PGSIZES;
+		if (info.flags & VFIO_IOMMU_INFO_CAPABILITIES) {
+			minsz = offsetofend(struct vfio_iommu_type1_info,
+					    cap_offset);
+			if (info.argsz < minsz)
+				return -EINVAL;
+			ret = vfio_iommu_type1_caps(iommu, &caps,
+						    info.argsz - sizeof(info));
+			if (ret)
+				return ret;
+		}
+		if (caps.size) {
+			if (info.argsz < sizeof(info) + caps.size) {
+				info.argsz = sizeof(info) + caps.size;
+				info.cap_offset = 0;
+			} else {
+				if (copy_to_user((void __user *)arg +
+						 sizeof(info), caps.buf,
+						 caps.size)) {
+					kfree(caps.buf);
+					return -EFAULT;
+				}
+
+				info.cap_offset = sizeof(info);
+			}
+			kfree(caps.buf);
+		}
+
+		info.flags |= VFIO_IOMMU_INFO_PGSIZES;
 
 		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
 
-- 
2.7.4