[PATCH v6 3/3] vhost: switch to arrays of feature bits

["Michael S. Tsirkin" <mst@redhat.com>]

The current interface where caller has to know in which 64 bit chunk
each bit is, is inelegant and fragile.
Let's simply use arrays of bits.
By using unroll macros text size grows only slightly.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/vhost/net.c   | 19 ++++++++++---------
 drivers/vhost/scsi.c  |  9 ++++++---
 drivers/vhost/test.c  |  6 +++++-
 drivers/vhost/vhost.h | 42 ++++++++++++++++++++++++++++++++++--------
 drivers/vhost/vsock.c | 10 ++++++----
 5 files changed, 61 insertions(+), 25 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index d057ea55f5ad..f8ed39337f56 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -69,15 +69,15 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
 
 #define VHOST_DMA_IS_DONE(len) ((__force u32)(len) >= (__force u32)VHOST_DMA_DONE_LEN)
 
-static const u64 vhost_net_features[VIRTIO_FEATURES_U64S] = {
-	VHOST_FEATURES |
-	(1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
-	(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
-	(1ULL << VIRTIO_F_ACCESS_PLATFORM) |
-	(1ULL << VIRTIO_F_RING_RESET) |
-	(1ULL << VIRTIO_F_IN_ORDER),
-	VIRTIO_BIT(VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) |
-	VIRTIO_BIT(VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO),
+static const int vhost_net_bits[] = {
+	VHOST_FEATURES,
+	VHOST_NET_F_VIRTIO_NET_HDR,
+	VIRTIO_NET_F_MRG_RXBUF,
+	VIRTIO_F_ACCESS_PLATFORM,
+	VIRTIO_F_RING_RESET,
+	VIRTIO_F_IN_ORDER,
+	VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO,
+	VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO
 };
 
 enum {
@@ -1720,6 +1720,7 @@ static long vhost_net_set_owner(struct vhost_net *n)
 static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 			    unsigned long arg)
 {
+	const DEFINE_VHOST_FEATURES_ARRAY(vhost_net_features, vhost_net_bits);
 	u64 all_features[VIRTIO_FEATURES_U64S];
 	struct vhost_net *n = f->private_data;
 	void __user *argp = (void __user *)arg;
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 98e4f68f4e3c..f43c1fe9fad9 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -197,11 +197,14 @@ enum {
 };
 
 /* Note: can't set VIRTIO_F_VERSION_1 yet, since that implies ANY_LAYOUT. */
-enum {
-	VHOST_SCSI_FEATURES = VHOST_FEATURES | (1ULL << VIRTIO_SCSI_F_HOTPLUG) |
-					       (1ULL << VIRTIO_SCSI_F_T10_PI)
+static const int vhost_scsi_bits[] = {
+	VHOST_FEATURES,
+	VIRTIO_SCSI_F_HOTPLUG,
+	VIRTIO_SCSI_F_T10_PI
 };
 
+#define VHOST_SCSI_FEATURES VHOST_FEATURES_U64(vhost_scsi_bits, 0)
+
 #define VHOST_SCSI_MAX_TARGET	256
 #define VHOST_SCSI_MAX_IO_VQ	1024
 #define VHOST_SCSI_MAX_EVENT	128
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 94cd09f36f59..f592b2f548e8 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -28,7 +28,11 @@
  */
 #define VHOST_TEST_PKT_WEIGHT 256
 
-#define VHOST_TEST_FEATURES VHOST_FEATURES
+static const int vhost_test_bits[] = {
+	VHOST_FEATURES
+};
+
+#define VHOST_TEST_FEATURES VHOST_FEATURES_U64(vhost_test_features, 0)
 
 enum {
 	VHOST_TEST_VQ = 0,
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 621a6d9a8791..c7b92730668e 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -14,6 +14,7 @@
 #include <linux/atomic.h>
 #include <linux/vhost_iotlb.h>
 #include <linux/irqbypass.h>
+#include <linux/unroll.h>
 
 struct vhost_work;
 struct vhost_task;
@@ -279,14 +280,39 @@ void vhost_iotlb_map_free(struct vhost_iotlb *iotlb,
 				eventfd_signal((vq)->error_ctx);\
 	} while (0)
 
-enum {
-	VHOST_FEATURES = (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
-			 (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
-			 (1ULL << VIRTIO_RING_F_EVENT_IDX) |
-			 (1ULL << VHOST_F_LOG_ALL) |
-			 (1ULL << VIRTIO_F_ANY_LAYOUT) |
-			 (1ULL << VIRTIO_F_VERSION_1)
-};
+#define VHOST_FEATURES \
+	VIRTIO_F_NOTIFY_ON_EMPTY, \
+	VIRTIO_RING_F_INDIRECT_DESC, \
+	VIRTIO_RING_F_EVENT_IDX, \
+	VHOST_F_LOG_ALL, \
+	VIRTIO_F_ANY_LAYOUT, \
+	VIRTIO_F_VERSION_1
+
+static inline u64 vhost_features_u64(const int *features, int size, int idx)
+{
+	u64 res = 0;
+
+	unrolled_count(VIRTIO_FEATURES_BITS)
+	for (int i = 0; i < size; ++i) {
+		int bit = features[i];
+
+		if (virtio_features_chk_bit(bit) && VIRTIO_U64(bit) == idx)
+			res |= VIRTIO_BIT(bit);
+	}
+	return res;
+}
+
+#define VHOST_FEATURES_U64(features, idx) \
+	vhost_features_u64(features, ARRAY_SIZE(features), idx)
+
+#define DEFINE_VHOST_FEATURES_ARRAY_ENTRY(idx, features) \
+	[idx] = VHOST_FEATURES_U64(features, idx),
+
+#define DEFINE_VHOST_FEATURES_ARRAY(array, features) \
+	u64 array[VIRTIO_FEATURES_U64S] = { \
+		UNROLL(VIRTIO_FEATURES_U64S, \
+		       DEFINE_VHOST_FEATURES_ARRAY_ENTRY, features) \
+	}
 
 /**
  * vhost_vq_set_backend - Set backend.
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index ae01457ea2cd..0298ddc34824 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -29,12 +29,14 @@
  */
 #define VHOST_VSOCK_PKT_WEIGHT 256
 
-enum {
-	VHOST_VSOCK_FEATURES = VHOST_FEATURES |
-			       (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
-			       (1ULL << VIRTIO_VSOCK_F_SEQPACKET)
+static const int vhost_vsock_bits[] = {
+	VHOST_FEATURES,
+	VIRTIO_F_ACCESS_PLATFORM,
+	VIRTIO_VSOCK_F_SEQPACKET
 };
 
+#define VHOST_VSOCK_FEATURES VHOST_FEATURES_U64(vhost_vsock_bits, 0)
+
 enum {
 	VHOST_VSOCK_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)
 };
-- 
MST