vringh: support VA with iotlb

vDPA supports the possibility to use user VA in the iotlb messages.
So, let's add support for user VA in vringh to use it in the vDPA
simulators.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20230404131716.45855-1-sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vringh.c

@@ -1094,10 +1094,17 @@ EXPORT_SYMBOL(vringh_need_notify_kern);
 
 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
 
+struct iotlb_vec {
+	union {
+		struct iovec *iovec;
+		struct bio_vec *bvec;
+	} iov;
+	size_t count;
+};
+
 static int iotlb_translate(const struct vringh *vrh,
 			   u64 addr, u64 len, u64 *translated,
-			   struct bio_vec iov[],
-			   int iov_size, u32 perm)
+			   struct iotlb_vec *ivec, u32 perm)
 {
 	struct vhost_iotlb_map *map;
 	struct vhost_iotlb *iotlb = vrh->iotlb;
@@ -1107,9 +1114,11 @@ static int iotlb_translate(const struct vringh *vrh,
 	spin_lock(vrh->iotlb_lock);
 
 	while (len > s) {
-		u64 size, pa, pfn;
+		uintptr_t io_addr;
+		size_t io_len;
+		u64 size;
 
-		if (unlikely(ret >= iov_size)) {
+		if (unlikely(ret >= ivec->count)) {
 			ret = -ENOBUFS;
 			break;
 		}
@@ -1124,10 +1133,22 @@ static int iotlb_translate(const struct vringh *vrh,
 		}
 
 		size = map->size - addr + map->start;
-		pa = map->addr + addr - map->start;
-		pfn = pa >> PAGE_SHIFT;
-		bvec_set_page(&iov[ret], pfn_to_page(pfn), min(len - s, size),
-			      pa & (PAGE_SIZE - 1));
+		io_len = min(len - s, size);
+		io_addr = map->addr - map->start + addr;
+
+		if (vrh->use_va) {
+			struct iovec *iovec = ivec->iov.iovec;
+
+			iovec[ret].iov_len = io_len;
+			iovec[ret].iov_base = (void __user *)io_addr;
+		} else {
+			u64 pfn = io_addr >> PAGE_SHIFT;
+			struct bio_vec *bvec = ivec->iov.bvec;
+
+			bvec_set_page(&bvec[ret], pfn_to_page(pfn), io_len,
+				      io_addr & (PAGE_SIZE - 1));
+		}
+
 		s += size;
 		addr += size;
 		++ret;
@@ -1146,23 +1167,36 @@ static int iotlb_translate(const struct vringh *vrh,
 static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
 				  void *src, size_t len)
 {
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec[IOTLB_IOV_STRIDE];
+		struct bio_vec bvec[IOTLB_IOV_STRIDE];
+	} iov;
 	u64 total_translated = 0;
 
+	ivec.iov.iovec = iov.iovec;
+	ivec.count = IOTLB_IOV_STRIDE;
+
 	while (total_translated < len) {
-		struct bio_vec iov[IOTLB_IOV_STRIDE];
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
 
 		ret = iotlb_translate(vrh, (u64)(uintptr_t)src,
 				      len - total_translated, &translated,
-				      iov, ARRAY_SIZE(iov), VHOST_MAP_RO);
+				      &ivec, VHOST_MAP_RO);
 		if (ret == -ENOBUFS)
-			ret = ARRAY_SIZE(iov);
+			ret = IOTLB_IOV_STRIDE;
 		else if (ret < 0)
 			return ret;
 
-		iov_iter_bvec(&iter, ITER_SOURCE, iov, ret, translated);
+		if (vrh->use_va) {
+			iov_iter_init(&iter, ITER_SOURCE, ivec.iov.iovec, ret,
+				      translated);
+		} else {
+			iov_iter_bvec(&iter, ITER_SOURCE, ivec.iov.bvec, ret,
+				      translated);
+		}
 
 		ret = copy_from_iter(dst, translated, &iter);
 		if (ret < 0)
@@ -1179,23 +1213,36 @@ static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
 static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 				void *src, size_t len)
 {
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec[IOTLB_IOV_STRIDE];
+		struct bio_vec bvec[IOTLB_IOV_STRIDE];
+	} iov;
 	u64 total_translated = 0;
 
+	ivec.iov.iovec = iov.iovec;
+	ivec.count = IOTLB_IOV_STRIDE;
+
 	while (total_translated < len) {
-		struct bio_vec iov[IOTLB_IOV_STRIDE];
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
 
 		ret = iotlb_translate(vrh, (u64)(uintptr_t)dst,
 				      len - total_translated, &translated,
-				      iov, ARRAY_SIZE(iov), VHOST_MAP_WO);
+				      &ivec, VHOST_MAP_WO);
 		if (ret == -ENOBUFS)
-			ret = ARRAY_SIZE(iov);
+			ret = IOTLB_IOV_STRIDE;
 		else if (ret < 0)
 			return ret;
 
-		iov_iter_bvec(&iter, ITER_DEST, iov, ret, translated);
+		if (vrh->use_va) {
+			iov_iter_init(&iter, ITER_DEST, ivec.iov.iovec, ret,
+				      translated);
+		} else {
+			iov_iter_bvec(&iter, ITER_DEST, ivec.iov.bvec, ret,
+				      translated);
+		}
 
 		ret = copy_to_iter(src, translated, &iter);
 		if (ret < 0)
@@ -1212,20 +1259,36 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 static inline int getu16_iotlb(const struct vringh *vrh,
 			       u16 *val, const __virtio16 *p)
 {
-	struct bio_vec iov;
-	void *kaddr, *from;
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec[1];
+		struct bio_vec bvec[1];
+	} iov;
+	__virtio16 tmp;
 	int ret;
 
+	ivec.iov.iovec = iov.iovec;
+	ivec.count = 1;
+
 	/* Atomic read is needed for getu16 */
-	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
-			      &iov, 1, VHOST_MAP_RO);
+	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
+			      NULL, &ivec, VHOST_MAP_RO);
 	if (ret < 0)
 		return ret;
 
-	kaddr = kmap_local_page(iov.bv_page);
-	from = kaddr + iov.bv_offset;
-	*val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
-	kunmap_local(kaddr);
+	if (vrh->use_va) {
+		ret = __get_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
+		if (ret)
+			return ret;
+	} else {
+		void *kaddr = kmap_local_page(ivec.iov.bvec[0].bv_page);
+		void *from = kaddr + ivec.iov.bvec[0].bv_offset;
+
+		tmp = READ_ONCE(*(__virtio16 *)from);
+		kunmap_local(kaddr);
+	}
+
+	*val = vringh16_to_cpu(vrh, tmp);
 
 	return 0;
 }
@@ -1233,20 +1296,36 @@ static inline int getu16_iotlb(const struct vringh *vrh,
 static inline int putu16_iotlb(const struct vringh *vrh,
 			       __virtio16 *p, u16 val)
 {
-	struct bio_vec iov;
-	void *kaddr, *to;
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec;
+		struct bio_vec bvec;
+	} iov;
+	__virtio16 tmp;
 	int ret;
 
+	ivec.iov.iovec = &iov.iovec;
+	ivec.count = 1;
+
 	/* Atomic write is needed for putu16 */
-	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
-			      &iov, 1, VHOST_MAP_WO);
+	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
+			      NULL, &ivec, VHOST_MAP_RO);
 	if (ret < 0)
 		return ret;
 
-	kaddr = kmap_local_page(iov.bv_page);
-	to = kaddr + iov.bv_offset;
-	WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
-	kunmap_local(kaddr);
+	tmp = cpu_to_vringh16(vrh, val);
+
+	if (vrh->use_va) {
+		ret = __put_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
+		if (ret)
+			return ret;
+	} else {
+		void *kaddr = kmap_local_page(ivec.iov.bvec[0].bv_page);
+		void *to = kaddr + ivec.iov.bvec[0].bv_offset;
+
+		WRITE_ONCE(*(__virtio16 *)to, tmp);
+		kunmap_local(kaddr);
+	}
 
 	return 0;
 }
@@ -1320,11 +1399,39 @@ int vringh_init_iotlb(struct vringh *vrh, u64 features,
 		      struct vring_avail *avail,
 		      struct vring_used *used)
 {
+	vrh->use_va = false;
+
 	return vringh_init_kern(vrh, features, num, weak_barriers,
 				desc, avail, used);
 }
 EXPORT_SYMBOL(vringh_init_iotlb);
 
+/**
+ * vringh_init_iotlb_va - initialize a vringh for a ring with IOTLB containing
+ *                        user VA.
+ * @vrh: the vringh to initialize.
+ * @features: the feature bits for this ring.
+ * @num: the number of elements.
+ * @weak_barriers: true if we only need memory barriers, not I/O.
+ * @desc: the userspace descriptor pointer.
+ * @avail: the userspace avail pointer.
+ * @used: the userspace used pointer.
+ *
+ * Returns an error if num is invalid.
+ */
+int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
+			 unsigned int num, bool weak_barriers,
+			 struct vring_desc *desc,
+			 struct vring_avail *avail,
+			 struct vring_used *used)
+{
+	vrh->use_va = true;
+
+	return vringh_init_kern(vrh, features, num, weak_barriers,
+				desc, avail, used);
+}
+EXPORT_SYMBOL(vringh_init_iotlb_va);
+
 /**
  * vringh_set_iotlb - initialize a vringh for a ring with IOTLB.
  * @vrh: the vring

include/linux/vringh.h

@@ -32,6 +32,9 @@ struct vringh {
 	/* Can we get away with weak barriers? */
 	bool weak_barriers;
 
+	/* Use user's VA */
+	bool use_va;
+
 	/* Last available index we saw (ie. where we're up to). */
 	u16 last_avail_idx;
 
@@ -284,6 +287,12 @@ int vringh_init_iotlb(struct vringh *vrh, u64 features,
 		      struct vring_avail *avail,
 		      struct vring_used *used);
 
+int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
+			 unsigned int num, bool weak_barriers,
+			 struct vring_desc *desc,
+			 struct vring_avail *avail,
+			 struct vring_used *used);
+
 int vringh_getdesc_iotlb(struct vringh *vrh,
 			 struct vringh_kiov *riov,
 			 struct vringh_kiov *wiov,