[RFC PATCH v5 04/11] VFIO_IOMMU_TYPE1: Introduce the VFIO_DMA_MAP_FLAG_EXEC flag

[Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>]

The ARM SMMU driver expects the IOMMU_EXEC flag, otherwise it will
set the page tables for a device as XN (execute never). This affects
devices such as the ARM PL330 DMA Controller, which fails to operate
if the XN flag is set on the memory it tries to fetch its instructions
from.

We introduce the VFIO_DMA_MAP_FLAG_EXEC to VFIO, and use it in
VFIO_IOMMU_TYPE1 to set the IOMMU_EXEC flag. This way the user can
control whether the XN flag will be set on the requested mappings. If
the IOMMU_EXEC flag is available for at least one IOMMU of a container,
the new capability VFIO_IOMMU_PROT_EXEC will be exposed.

Signed-off-by: Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>
---
 drivers/vfio/vfio_iommu_type1.c | 34 +++++++++++++++++++++++++++++++---
 include/uapi/linux/vfio.h       |  2 ++
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 4dc989d..6ce32bf 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -498,12 +498,15 @@ static int map_try_harder(struct vfio_domain *domain, dma_addr_t iova,
 }
 
 static int vfio_iommu_map(struct vfio_iommu *iommu, dma_addr_t iova,
-			  unsigned long pfn, long npage, int prot)
+			  unsigned long pfn, long npage, int prot, bool exec)
 {
 	struct vfio_domain *d;
 	int ret;
 
 	list_for_each_entry(d, &iommu->domain_list, next) {
+		if (exec && iommu_domain_has_cap(d->domain, IOMMU_CAP_DMA_EXEC))
+			prot |= IOMMU_EXEC;
+
 		ret = iommu_map(d->domain, iova, (phys_addr_t)pfn << PAGE_SHIFT,
 				npage << PAGE_SHIFT, prot | d->prot);
 		if (ret) {
@@ -530,6 +533,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	size_t size = map->size;
 	long npage;
 	int ret = 0, prot = 0;
+	bool prot_exec = false;
 	uint64_t mask;
 	struct vfio_dma *dma;
 	unsigned long pfn;
@@ -543,6 +547,8 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 		prot |= IOMMU_WRITE;
 	if (map->flags & VFIO_DMA_MAP_FLAG_READ)
 		prot |= IOMMU_READ;
+	if (map->flags & VFIO_DMA_MAP_FLAG_EXEC)
+		prot_exec = true;
 
 	if (!prot)
 		return -EINVAL; /* No READ/WRITE? */
@@ -595,7 +601,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 		}
 
 		/* Map it! */
-		ret = vfio_iommu_map(iommu, iova, pfn, npage, prot);
+		ret = vfio_iommu_map(iommu, iova, pfn, npage, prot, prot_exec);
 		if (ret) {
 			vfio_unpin_pages(pfn, npage, prot, true);
 			break;
@@ -887,6 +893,23 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
 	return ret;
 }
 
+static int vfio_domains_have_iommu_exec(struct vfio_iommu *iommu)
+{
+	struct vfio_domain *d;
+	int ret = 0;
+
+	mutex_lock(&iommu->lock);
+	list_for_each_entry(d, &iommu->domain_list, next) {
+		if (iommu_domain_has_cap(d->domain, IOMMU_CAP_DMA_EXEC)) {
+			ret = 1;
+			break;
+		}
+	}
+	mutex_unlock(&iommu->lock);
+
+	return ret;
+}
+
 static long vfio_iommu_type1_ioctl(void *iommu_data,
 				   unsigned int cmd, unsigned long arg)
 {
@@ -902,6 +925,10 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 			if (!iommu)
 				return 0;
 			return vfio_domains_have_iommu_cache(iommu);
+		case VFIO_IOMMU_PROT_EXEC:
+			if (!iommu)
+				return 0;
+			return vfio_domains_have_iommu_exec(iommu);
 		default:
 			return 0;
 		}
@@ -925,7 +952,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 	} else if (cmd == VFIO_IOMMU_MAP_DMA) {
 		struct vfio_iommu_type1_dma_map map;
 		uint32_t mask = VFIO_DMA_MAP_FLAG_READ |
-				VFIO_DMA_MAP_FLAG_WRITE;
+				VFIO_DMA_MAP_FLAG_WRITE |
+				VFIO_DMA_MAP_FLAG_EXEC;
 
 		minsz = offsetofend(struct vfio_iommu_type1_dma_map, size);
 
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index cb9023d..0847b29 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -29,6 +29,7 @@
  * capability is subject to change as groups are added or removed.
  */
 #define VFIO_DMA_CC_IOMMU		4
+#define VFIO_IOMMU_PROT_EXEC		5
 
 /*
  * The IOCTL interface is designed for extensibility by embedding the
@@ -398,6 +399,7 @@ struct vfio_iommu_type1_dma_map {
 	__u32	flags;
 #define VFIO_DMA_MAP_FLAG_READ (1 << 0)		/* readable from device */
 #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1)	/* writable from device */
+#define VFIO_DMA_MAP_FLAG_EXEC (1 << 2)		/* executable from device */
 	__u64	vaddr;				/* Process virtual address */
 	__u64	iova;				/* IO virtual address */
 	__u64	size;				/* Size of mapping (bytes) */
-- 
1.8.3.2