[PATCH v6 0/3] virtio: feature related cleanups

[PATCH v6 0/3] virtio: feature related cleanups

[Michael S. Tsirkin]

Cleanup around handling of feature bits:
- address word/dword/qword confusion
- simplify interfaces so callers do not need to
  remember in which 64 bit chunk each bit belongs

changes from v5:
  rename variables in vhost to make the diff much smaller
changes from v4: address comments by Jason
  move features variable to beginning of block
  unsigned long -> u64 - they are not the same
changes from v3:
  drop an out of date unnecessary kdoc parser change

changes from v2:
- drop unnecessary casts
- rework the interface to use array of bits not


Michael S. Tsirkin (3):
  virtio: clean up features qword/dword terms
  vhost/test: add test specific macro for features
  vhost: switch to arrays of feature bits

 drivers/vhost/net.c                    | 29 +++++++++---------
 drivers/vhost/scsi.c                   |  9 ++++--
 drivers/vhost/test.c                   | 10 ++++--
 drivers/vhost/vhost.h                  | 42 +++++++++++++++++++++-----
 drivers/vhost/vsock.c                  | 10 +++---
 drivers/virtio/virtio.c                | 12 ++++----
 drivers/virtio/virtio_debug.c          | 10 +++---
 drivers/virtio/virtio_pci_modern_dev.c |  6 ++--
 include/linux/virtio.h                 |  2 +-
 include/linux/virtio_config.h          |  2 +-
 include/linux/virtio_features.h        | 29 +++++++++---------
 include/linux/virtio_pci_modern.h      |  8 ++---
 12 files changed, 104 insertions(+), 65 deletions(-)

-- 
MST

[PATCH v6 1/3] virtio: clean up features qword/dword terms

[Michael S. Tsirkin]

virtio pci uses word to mean "16 bits". mmio uses it to mean
"32 bits".

To avoid confusion, let's avoid the term in core virtio
altogether. Just say U64 to mean "64 bit".

Fixes: e7d4c1c5a546 ("virtio: introduce extended features")
Cc: Paolo Abeni <pabeni@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/vhost/net.c                    | 12 +++++------
 drivers/virtio/virtio.c                | 12 +++++------
 drivers/virtio/virtio_debug.c          | 10 ++++-----
 drivers/virtio/virtio_pci_modern_dev.c |  6 +++---
 include/linux/virtio.h                 |  2 +-
 include/linux/virtio_config.h          |  2 +-
 include/linux/virtio_features.h        | 29 +++++++++++++-------------
 include/linux/virtio_pci_modern.h      |  8 +++----
 8 files changed, 41 insertions(+), 40 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 35ded4330431..d057ea55f5ad 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -69,7 +69,7 @@ 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_DWORDS] = {
+static const u64 vhost_net_features[VIRTIO_FEATURES_U64S] = {
 	VHOST_FEATURES |
 	(1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
 	(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
@@ -1720,7 +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)
 {
-	u64 all_features[VIRTIO_FEATURES_DWORDS];
+	u64 all_features[VIRTIO_FEATURES_U64S];
 	struct vhost_net *n = f->private_data;
 	void __user *argp = (void __user *)arg;
 	u64 __user *featurep = argp;
@@ -1752,7 +1752,7 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 
 		/* Copy the net features, up to the user-provided buffer size */
 		argp += sizeof(u64);
-		copied = min(count, VIRTIO_FEATURES_DWORDS);
+		copied = min(count, (u64)VIRTIO_FEATURES_U64S);
 		if (copy_to_user(argp, vhost_net_features,
 				 copied * sizeof(u64)))
 			return -EFAULT;
@@ -1767,13 +1767,13 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 
 		virtio_features_zero(all_features);
 		argp += sizeof(u64);
-		copied = min(count, VIRTIO_FEATURES_DWORDS);
+		copied = min(count, (u64)VIRTIO_FEATURES_U64S);
 		if (copy_from_user(all_features, argp, copied * sizeof(u64)))
 			return -EFAULT;
 
 		/*
 		 * Any feature specified by user-space above
-		 * VIRTIO_FEATURES_MAX is not supported by definition.
+		 * VIRTIO_FEATURES_BITS is not supported by definition.
 		 */
 		for (i = copied; i < count; ++i) {
 			if (copy_from_user(&features, featurep + 1 + i,
@@ -1783,7 +1783,7 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 				return -EOPNOTSUPP;
 		}
 
-		for (i = 0; i < VIRTIO_FEATURES_DWORDS; i++)
+		for (i = 0; i < VIRTIO_FEATURES_U64S; i++)
 			if (all_features[i] & ~vhost_net_features[i])
 				return -EOPNOTSUPP;
 
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a09eb4d62f82..5bdc6b82b30b 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -53,7 +53,7 @@ static ssize_t features_show(struct device *_d,
 
 	/* We actually represent this as a bitstring, as it could be
 	 * arbitrary length in future. */
-	for (i = 0; i < VIRTIO_FEATURES_MAX; i++)
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++)
 		len += sysfs_emit_at(buf, len, "%c",
 			       __virtio_test_bit(dev, i) ? '1' : '0');
 	len += sysfs_emit_at(buf, len, "\n");
@@ -272,8 +272,8 @@ static int virtio_dev_probe(struct device *_d)
 	int err, i;
 	struct virtio_device *dev = dev_to_virtio(_d);
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
-	u64 device_features[VIRTIO_FEATURES_DWORDS];
-	u64 driver_features[VIRTIO_FEATURES_DWORDS];
+	u64 device_features[VIRTIO_FEATURES_U64S];
+	u64 driver_features[VIRTIO_FEATURES_U64S];
 	u64 driver_features_legacy;
 
 	/* We have a driver! */
@@ -286,7 +286,7 @@ static int virtio_dev_probe(struct device *_d)
 	virtio_features_zero(driver_features);
 	for (i = 0; i < drv->feature_table_size; i++) {
 		unsigned int f = drv->feature_table[i];
-		if (!WARN_ON_ONCE(f >= VIRTIO_FEATURES_MAX))
+		if (!WARN_ON_ONCE(f >= VIRTIO_FEATURES_BITS))
 			virtio_features_set_bit(driver_features, f);
 	}
 
@@ -303,7 +303,7 @@ static int virtio_dev_probe(struct device *_d)
 	}
 
 	if (virtio_features_test_bit(device_features, VIRTIO_F_VERSION_1)) {
-		for (i = 0; i < VIRTIO_FEATURES_DWORDS; ++i)
+		for (i = 0; i < VIRTIO_FEATURES_U64S; ++i)
 			dev->features_array[i] = driver_features[i] &
 						 device_features[i];
 	} else {
@@ -325,7 +325,7 @@ static int virtio_dev_probe(struct device *_d)
 		goto err;
 
 	if (drv->validate) {
-		u64 features[VIRTIO_FEATURES_DWORDS];
+		u64 features[VIRTIO_FEATURES_U64S];
 
 		virtio_features_copy(features, dev->features_array);
 		err = drv->validate(dev);
diff --git a/drivers/virtio/virtio_debug.c b/drivers/virtio/virtio_debug.c
index d58713ddf2e5..ccf1955a1183 100644
--- a/drivers/virtio/virtio_debug.c
+++ b/drivers/virtio/virtio_debug.c
@@ -8,12 +8,12 @@ static struct dentry *virtio_debugfs_dir;
 
 static int virtio_debug_device_features_show(struct seq_file *s, void *data)
 {
-	u64 device_features[VIRTIO_FEATURES_DWORDS];
+	u64 device_features[VIRTIO_FEATURES_U64S];
 	struct virtio_device *dev = s->private;
 	unsigned int i;
 
 	virtio_get_features(dev, device_features);
-	for (i = 0; i < VIRTIO_FEATURES_MAX; i++) {
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
 		if (virtio_features_test_bit(device_features, i))
 			seq_printf(s, "%u\n", i);
 	}
@@ -26,7 +26,7 @@ static int virtio_debug_filter_features_show(struct seq_file *s, void *data)
 	struct virtio_device *dev = s->private;
 	unsigned int i;
 
-	for (i = 0; i < VIRTIO_FEATURES_MAX; i++) {
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
 		if (virtio_features_test_bit(dev->debugfs_filter_features, i))
 			seq_printf(s, "%u\n", i);
 	}
@@ -50,7 +50,7 @@ static int virtio_debug_filter_feature_add(void *data, u64 val)
 {
 	struct virtio_device *dev = data;
 
-	if (val >= VIRTIO_FEATURES_MAX)
+	if (val >= VIRTIO_FEATURES_BITS)
 		return -EINVAL;
 
 	virtio_features_set_bit(dev->debugfs_filter_features, val);
@@ -64,7 +64,7 @@ static int virtio_debug_filter_feature_del(void *data, u64 val)
 {
 	struct virtio_device *dev = data;
 
-	if (val >= VIRTIO_FEATURES_MAX)
+	if (val >= VIRTIO_FEATURES_BITS)
 		return -EINVAL;
 
 	virtio_features_clear_bit(dev->debugfs_filter_features, val);
diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index 9e503b7a58d8..413a8c353463 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c
@@ -401,7 +401,7 @@ void vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
 	int i;
 
 	virtio_features_zero(features);
-	for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+	for (i = 0; i < VIRTIO_FEATURES_BITS / 32; i++) {
 		u64 cur;
 
 		vp_iowrite32(i, &cfg->device_feature_select);
@@ -427,7 +427,7 @@ vp_modern_get_driver_extended_features(struct virtio_pci_modern_device *mdev,
 	int i;
 
 	virtio_features_zero(features);
-	for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+	for (i = 0; i < VIRTIO_FEATURES_BITS / 32; i++) {
 		u64 cur;
 
 		vp_iowrite32(i, &cfg->guest_feature_select);
@@ -448,7 +448,7 @@ void vp_modern_set_extended_features(struct virtio_pci_modern_device *mdev,
 	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
 	int i;
 
-	for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+	for (i = 0; i < VIRTIO_FEATURES_BITS / 32; i++) {
 		u32 cur = features[i >> 1] >> (32 * (i & 1));
 
 		vp_iowrite32(i, &cfg->guest_feature_select);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 96c66126c074..132a474e5914 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -177,7 +177,7 @@ struct virtio_device {
 	union virtio_map vmap;
 #ifdef CONFIG_VIRTIO_DEBUG
 	struct dentry *debugfs_dir;
-	u64 debugfs_filter_features[VIRTIO_FEATURES_DWORDS];
+	u64 debugfs_filter_features[VIRTIO_FEATURES_U64S];
 #endif
 };
 
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index a1af2676bbe6..69f84ea85d71 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -80,7 +80,7 @@ struct virtqueue_info {
  *	Returns the first 64 feature bits.
  * @get_extended_features:
  *      vdev: the virtio_device
- *      Returns the first VIRTIO_FEATURES_MAX feature bits (all we currently
+ *      Returns the first VIRTIO_FEATURES_BITS feature bits (all we currently
  *      need).
  * @finalize_features: confirm what device features we'll be using.
  *	vdev: the virtio_device
diff --git a/include/linux/virtio_features.h b/include/linux/virtio_features.h
index f748f2f87de8..ea2ad8717882 100644
--- a/include/linux/virtio_features.h
+++ b/include/linux/virtio_features.h
@@ -4,15 +4,16 @@
 
 #include <linux/bits.h>
 
-#define VIRTIO_FEATURES_DWORDS	2
-#define VIRTIO_FEATURES_MAX	(VIRTIO_FEATURES_DWORDS * 64)
-#define VIRTIO_FEATURES_WORDS	(VIRTIO_FEATURES_DWORDS * 2)
+#define VIRTIO_FEATURES_U64S	2
+#define VIRTIO_FEATURES_BITS	(VIRTIO_FEATURES_U64S * 64)
+
 #define VIRTIO_BIT(b)		BIT_ULL((b) & 0x3f)
-#define VIRTIO_DWORD(b)		((b) >> 6)
+#define VIRTIO_U64(b)		((b) >> 6)
+
 #define VIRTIO_DECLARE_FEATURES(name)			\
 	union {						\
 		u64 name;				\
-		u64 name##_array[VIRTIO_FEATURES_DWORDS];\
+		u64 name##_array[VIRTIO_FEATURES_U64S];\
 	}
 
 static inline bool virtio_features_chk_bit(unsigned int bit)
@@ -22,9 +23,9 @@ static inline bool virtio_features_chk_bit(unsigned int bit)
 		 * Don't care returning the correct value: the build
 		 * will fail before any bad features access
 		 */
-		BUILD_BUG_ON(bit >= VIRTIO_FEATURES_MAX);
+		BUILD_BUG_ON(bit >= VIRTIO_FEATURES_BITS);
 	} else {
-		if (WARN_ON_ONCE(bit >= VIRTIO_FEATURES_MAX))
+		if (WARN_ON_ONCE(bit >= VIRTIO_FEATURES_BITS))
 			return false;
 	}
 	return true;
@@ -34,26 +35,26 @@ static inline bool virtio_features_test_bit(const u64 *features,
 					    unsigned int bit)
 {
 	return virtio_features_chk_bit(bit) &&
-	       !!(features[VIRTIO_DWORD(bit)] & VIRTIO_BIT(bit));
+	       !!(features[VIRTIO_U64(bit)] & VIRTIO_BIT(bit));
 }
 
 static inline void virtio_features_set_bit(u64 *features,
 					   unsigned int bit)
 {
 	if (virtio_features_chk_bit(bit))
-		features[VIRTIO_DWORD(bit)] |= VIRTIO_BIT(bit);
+		features[VIRTIO_U64(bit)] |= VIRTIO_BIT(bit);
 }
 
 static inline void virtio_features_clear_bit(u64 *features,
 					     unsigned int bit)
 {
 	if (virtio_features_chk_bit(bit))
-		features[VIRTIO_DWORD(bit)] &= ~VIRTIO_BIT(bit);
+		features[VIRTIO_U64(bit)] &= ~VIRTIO_BIT(bit);
 }
 
 static inline void virtio_features_zero(u64 *features)
 {
-	memset(features, 0, sizeof(features[0]) * VIRTIO_FEATURES_DWORDS);
+	memset(features, 0, sizeof(features[0]) * VIRTIO_FEATURES_U64S);
 }
 
 static inline void virtio_features_from_u64(u64 *features, u64 from)
@@ -66,7 +67,7 @@ static inline bool virtio_features_equal(const u64 *f1, const u64 *f2)
 {
 	int i;
 
-	for (i = 0; i < VIRTIO_FEATURES_DWORDS; ++i)
+	for (i = 0; i < VIRTIO_FEATURES_U64S; ++i)
 		if (f1[i] != f2[i])
 			return false;
 	return true;
@@ -74,14 +75,14 @@ static inline bool virtio_features_equal(const u64 *f1, const u64 *f2)
 
 static inline void virtio_features_copy(u64 *to, const u64 *from)
 {
-	memcpy(to, from, sizeof(to[0]) * VIRTIO_FEATURES_DWORDS);
+	memcpy(to, from, sizeof(to[0]) * VIRTIO_FEATURES_U64S);
 }
 
 static inline void virtio_features_andnot(u64 *to, const u64 *f1, const u64 *f2)
 {
 	int i;
 
-	for (i = 0; i < VIRTIO_FEATURES_DWORDS; i++)
+	for (i = 0; i < VIRTIO_FEATURES_U64S; i++)
 		to[i] = f1[i] & ~f2[i];
 }
 
diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
index 48bc12d1045b..9a3f2fc53bd6 100644
--- a/include/linux/virtio_pci_modern.h
+++ b/include/linux/virtio_pci_modern.h
@@ -107,7 +107,7 @@ void vp_modern_set_extended_features(struct virtio_pci_modern_device *mdev,
 static inline u64
 vp_modern_get_features(struct virtio_pci_modern_device *mdev)
 {
-	u64 features_array[VIRTIO_FEATURES_DWORDS];
+	u64 features_array[VIRTIO_FEATURES_U64S];
 
 	vp_modern_get_extended_features(mdev, features_array);
 	return features_array[0];
@@ -116,11 +116,11 @@ vp_modern_get_features(struct virtio_pci_modern_device *mdev)
 static inline u64
 vp_modern_get_driver_features(struct virtio_pci_modern_device *mdev)
 {
-	u64 features_array[VIRTIO_FEATURES_DWORDS];
+	u64 features_array[VIRTIO_FEATURES_U64S];
 	int i;
 
 	vp_modern_get_driver_extended_features(mdev, features_array);
-	for (i = 1; i < VIRTIO_FEATURES_DWORDS; ++i)
+	for (i = 1; i < VIRTIO_FEATURES_U64S; ++i)
 		WARN_ON_ONCE(features_array[i]);
 	return features_array[0];
 }
@@ -128,7 +128,7 @@ vp_modern_get_driver_features(struct virtio_pci_modern_device *mdev)
 static inline void
 vp_modern_set_features(struct virtio_pci_modern_device *mdev, u64 features)
 {
-	u64 features_array[VIRTIO_FEATURES_DWORDS];
+	u64 features_array[VIRTIO_FEATURES_U64S];
 
 	virtio_features_from_u64(features_array, features);
 	vp_modern_set_extended_features(mdev, features_array);
-- 
MST

[PATCH v6 2/3] vhost/test: add test specific macro for features

[Michael S. Tsirkin]

test just uses vhost features with no change,
but people tend to copy/paste code, so let's
add our own define.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/vhost/test.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 42c955a5b211..94cd09f36f59 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -28,6 +28,8 @@
  */
 #define VHOST_TEST_PKT_WEIGHT 256
 
+#define VHOST_TEST_FEATURES VHOST_FEATURES
+
 enum {
 	VHOST_TEST_VQ = 0,
 	VHOST_TEST_VQ_MAX = 1,
@@ -328,14 +330,14 @@ static long vhost_test_ioctl(struct file *f, unsigned int ioctl,
 			return -EFAULT;
 		return vhost_test_set_backend(n, backend.index, backend.fd);
 	case VHOST_GET_FEATURES:
-		features = VHOST_FEATURES;
+		features = VHOST_TEST_FEATURES;
 		if (copy_to_user(featurep, &features, sizeof features))
 			return -EFAULT;
 		return 0;
 	case VHOST_SET_FEATURES:
 		if (copy_from_user(&features, featurep, sizeof features))
 			return -EFAULT;
-		if (features & ~VHOST_FEATURES)
+		if (features & ~VHOST_TEST_FEATURES)
 			return -EOPNOTSUPP;
 		return vhost_test_set_features(n, features);
 	case VHOST_RESET_OWNER:
-- 
MST

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

[Michael S. Tsirkin]

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

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

[Jason Wang]

On Thu, Nov 27, 2025 at 2:40 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> 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)

Did you mean vhost_test_bits actually?

Thanks

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

[Michael S. Tsirkin]

On Fri, Nov 28, 2025 at 10:39:57AM +0800, Jason Wang wrote:
> On Thu, Nov 27, 2025 at 2:40 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > 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)
> 
> Did you mean vhost_test_bits actually?
> 
> Thanks

indeed.