[PATCH v7 7/7] vfio/type1: return MSI mapping requirements with VFIO_IOMMU_GET_INFO

Eric Auger
2016-04-19T17:25:38Z

This patch allows the user-space to know whether MSI addresses need to
be mapped in the IOMMU. The user-space uses VFIO_IOMMU_GET_INFO ioctl and
IOMMU_INFO_REQUIRE_MSI_MAP gets set if they need to.

The computation of the number of IOVA pages to be provided by the user
space will be implemented in a separate patch using capability chains.

Signed-off-by: Eric Auger <eric.auger@linaro.org>

---
v6 -> v7:
- remove the computation of the number of IOVA pages to be provisionned.
This number depends on the domain/group/device topology which can
dynamically change. Let's rely instead rely on an arbitrary max depending
on the system

v4 -> v5:
- move msi_info and ret declaration within the conditional code

v3 -> v4:
- replace former vfio_domains_require_msi_mapping by
more complex computation of MSI mapping requirements, especially the
number of pages to be provided by the user-space.
- reword patch title

RFC v1 -> v1:
- derived from
[RFC PATCH 3/6] vfio: Extend iommu-info to return MSIs automap state
- renamed allow_msi_reconfig into require_msi_mapping
- fixed VFIO_IOMMU_GET_INFO
---
drivers/vfio/vfio_iommu_type1.c | 24 ++++++++++++++++++++++++
include/uapi/linux/vfio.h | 5 ++++-
2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 51b1f15..a63ce6f 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -310,6 +310,27 @@ static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
}

/*
+ * vfio_domains_require_msi_mapping: return whether MSI doorbells must be
+ * iommu mapped
+ *
+ * returns true if msi mapping is requested
+ */
+static bool vfio_domains_require_msi_mapping(struct vfio_iommu *iommu)
+{
+ struct vfio_domain *d;
+ bool flag;
+
+ mutex_lock(&iommu->lock);
+ /* All domains have same require_msi_map property, pick first */
+ d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
+ flag = (!(iommu_domain_get_attr(d->domain,
+ DOMAIN_ATTR_MSI_MAPPING, NULL)));
+
+ mutex_unlock(&iommu->lock);
+
+ return flag;
+}
+/*
* Attempt to pin pages. We really don't want to track all the pfns and
* the iommu can only map chunks of consecutive pfns anyway, so get the
* first page and all consecutive pages with the same locking.
@@ -1231,6 +1252,9 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,

info.flags = VFIO_IOMMU_INFO_PGSIZES;

+ if (vfio_domains_require_msi_mapping(iommu))
+ info.flags |= VFIO_IOMMU_INFO_REQUIRE_MSI_MAP;
+
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 0637f35..4d9c97d 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -488,6 +488,7 @@ struct vfio_iommu_type1_info {
__u32 argsz;
__u32 flags;
#define VFIO_IOMMU_INFO_PGSIZES (1 << 0) /* supported page sizes info */
+#define VFIO_IOMMU_INFO_REQUIRE_MSI_MAP (1 << 1)/* MSI must be mapped */
__u64 iova_pgsizes; /* Bitmap of supported page sizes */
};

@@ -501,7 +502,9 @@ struct vfio_iommu_type1_info {
*
* In case RESERVED_MSI_IOVA flag is set, the API only aims at registering an
* IOVA region that will be used on some platforms to map the host MSI frames.
- * In that specific case, vaddr is ignored.
+ * In that specific case, vaddr is ignored. The requirement for provisioning
+ * such reserved IOVA range can be checked by calling VFIO_IOMMU_GET_INFO and
+ * testing the VFIO_IOMMU_INFO_REQUIRE_MSI_MAP flag.
*/
struct vfio_iommu_type1_dma_map {
__u32 argsz;
--
1.9.1