[PATCH v2 0/2] virtio: feature related cleanups

[PATCH v2 0/2] virtio: feature related cleanups

[Michael S. Tsirkin]

A minor cleanup around handling of feature bits: this fixes
up terminology and adds build checks.

Lightly tested.

changes from v1:
	dropped using "word" completely


Michael S. Tsirkin (2):
  virtio: clean up features qword/dword terms
  vhost: use checked versions of VIRTIO_BIT

 drivers/vhost/net.c                    | 16 +++++------
 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        | 37 ++++++++++++++++----------
 include/linux/virtio_pci_modern.h      |  8 +++---
 scripts/lib/kdoc/kdoc_parser.py        |  2 +-
 9 files changed, 52 insertions(+), 43 deletions(-)

-- 
MST

[PATCH v2 1/2] 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>
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 +++----
 scripts/lib/kdoc/kdoc_parser.py        |  2 +-
 9 files changed, 42 insertions(+), 41 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 35ded4330431..afabc5cf31a6 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_ARRAY_SIZE] = {
 	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_ARRAY_SIZE];
 	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_ARRAY_SIZE);
 		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_ARRAY_SIZE);
 		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_ARRAY_SIZE; 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..49aa21a7443c 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_ARRAY_SIZE];
+	u64 driver_features[VIRTIO_FEATURES_ARRAY_SIZE];
 	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_ARRAY_SIZE; ++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_ARRAY_SIZE];
 
 		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..92055dc15860 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_ARRAY_SIZE];
 	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..9778adf8c6e3 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_ARRAY_SIZE];
 #endif
 };
 
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 16001e9f9b39..a9b7a5bc90ce 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..9c99014196ea 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_BITS	(128)
 #define VIRTIO_BIT(b)		BIT_ULL((b) & 0x3f)
-#define VIRTIO_DWORD(b)		((b) >> 6)
+#define VIRTIO_U64(b)		((b) >> 6)
+
+#define VIRTIO_FEATURES_ARRAY_SIZE VIRTIO_U64(VIRTIO_FEATURES_BITS)
+
 #define VIRTIO_DECLARE_FEATURES(name)			\
 	union {						\
 		u64 name;				\
-		u64 name##_array[VIRTIO_FEATURES_DWORDS];\
+		u64 name##_array[VIRTIO_FEATURES_ARRAY_SIZE];\
 	}
 
 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_ARRAY_SIZE);
 }
 
 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_ARRAY_SIZE; ++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_ARRAY_SIZE);
 }
 
 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_ARRAY_SIZE; 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..eba5977126ed 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_ARRAY_SIZE];
 
 	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_ARRAY_SIZE];
 	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_ARRAY_SIZE; ++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_ARRAY_SIZE];
 
 	virtio_features_from_u64(features_array, features);
 	vp_modern_set_extended_features(mdev, features_array);
diff --git a/scripts/lib/kdoc/kdoc_parser.py b/scripts/lib/kdoc/kdoc_parser.py
index fe730099eca8..5d629aebc8f0 100644
--- a/scripts/lib/kdoc/kdoc_parser.py
+++ b/scripts/lib/kdoc/kdoc_parser.py
@@ -638,7 +638,7 @@ class KernelDoc:
             (KernRe(r'(?:__)?DECLARE_FLEX_ARRAY\s*\(' + args_pattern + r',\s*' + args_pattern + r'\)', re.S), r'\1 \2[]'),
             (KernRe(r'DEFINE_DMA_UNMAP_ADDR\s*\(' + args_pattern + r'\)', re.S), r'dma_addr_t \1'),
             (KernRe(r'DEFINE_DMA_UNMAP_LEN\s*\(' + args_pattern + r'\)', re.S), r'__u32 \1'),
-            (KernRe(r'VIRTIO_DECLARE_FEATURES\s*\(' + args_pattern + r'\)', re.S), r'u64 \1; u64 \1_array[VIRTIO_FEATURES_DWORDS]'),
+            (KernRe(r'VIRTIO_DECLARE_FEATURES\s*\(' + args_pattern + r'\)', re.S), r'u64 \1; u64 \1_array[VIRTIO_FEATURES_QWORDS]'),
         ]
 
         # Regexes here are guaranteed to have the end limiter matching
-- 
MST

[PATCH v2 2/2] vhost: use checked versions of VIRTIO_BIT

[Michael S. Tsirkin]

This adds compile-time checked versions of VIRTIO_BIT that set bits in
low and high qword, respectively.  Will prevent confusion when people
set bits in the wrong qword.

Cc: "Paolo Abeni" <pabeni@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/vhost/net.c             | 4 ++--
 include/linux/virtio_features.h | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index afabc5cf31a6..e208bb0ca7da 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -76,8 +76,8 @@ static const u64 vhost_net_features[VIRTIO_FEATURES_ARRAY_SIZE] = {
 	(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),
+	VIRTIO_BIT_HI(VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) |
+	VIRTIO_BIT_HI(VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO),
 };
 
 enum {
diff --git a/include/linux/virtio_features.h b/include/linux/virtio_features.h
index 9c99014196ea..2eaee0b7c2df 100644
--- a/include/linux/virtio_features.h
+++ b/include/linux/virtio_features.h
@@ -8,6 +8,14 @@
 #define VIRTIO_BIT(b)		BIT_ULL((b) & 0x3f)
 #define VIRTIO_U64(b)		((b) >> 6)
 
+/* Get a given feature bit in a given u64 entry. */
+#define VIRTIO_BIT_U64(bit, entry) \
+	(BUILD_BUG_ON_ZERO(const_true(VIRTIO_U64(bit) != (qword))) + \
+	 BIT_ULL((bit) - 64 * (entry)))
+
+#define VIRTIO_BIT_LO(b) VIRTIO_BIT_U64(b, 0)
+#define VIRTIO_BIT_HI(b) VIRTIO_BIT_U64(b, 1)
+
 #define VIRTIO_FEATURES_ARRAY_SIZE VIRTIO_U64(VIRTIO_FEATURES_BITS)
 
 #define VIRTIO_DECLARE_FEATURES(name)			\
-- 
MST

Re: [PATCH v2 1/2] virtio: clean up features qword/dword terms

[Andrew Lunn]

> @@ -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_ARRAY_SIZE);

Why is the cast needed? Why was 2 O.K, but (128 >> 6) needs a cast?

> -#define VIRTIO_FEATURES_DWORDS	2
> -#define VIRTIO_FEATURES_MAX	(VIRTIO_FEATURES_DWORDS * 64)
> -#define VIRTIO_FEATURES_WORDS	(VIRTIO_FEATURES_DWORDS * 2)
> +#define VIRTIO_FEATURES_BITS	(128)
>  #define VIRTIO_BIT(b)		BIT_ULL((b) & 0x3f)
> -#define VIRTIO_DWORD(b)		((b) >> 6)
> +#define VIRTIO_U64(b)		((b) >> 6)
> +
> +#define VIRTIO_FEATURES_ARRAY_SIZE VIRTIO_U64(VIRTIO_FEATURES_BITS)

	Andrew

Re: [PATCH v2 1/2] virtio: clean up features qword/dword terms

[Michael S. Tsirkin]

On Wed, Oct 22, 2025 at 04:20:52AM +0200, Andrew Lunn wrote:
> > @@ -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_ARRAY_SIZE);
> 
> Why is the cast needed? Why was 2 O.K, but (128 >> 6) needs a cast?

It's not - a leftover from one of the approaches I tried, thanks!

> > -#define VIRTIO_FEATURES_DWORDS	2
> > -#define VIRTIO_FEATURES_MAX	(VIRTIO_FEATURES_DWORDS * 64)
> > -#define VIRTIO_FEATURES_WORDS	(VIRTIO_FEATURES_DWORDS * 2)
> > +#define VIRTIO_FEATURES_BITS	(128)
> >  #define VIRTIO_BIT(b)		BIT_ULL((b) & 0x3f)
> > -#define VIRTIO_DWORD(b)		((b) >> 6)
> > +#define VIRTIO_U64(b)		((b) >> 6)
> > +
> > +#define VIRTIO_FEATURES_ARRAY_SIZE VIRTIO_U64(VIRTIO_FEATURES_BITS)
> 
> 	Andrew