virtio: use u32, not bitmap for features

It seemed like a good idea to use bitmap for features
in struct virtio_device, but it's actually a pain,
and seems to become even more painful when we get more
than 32 feature bits.  Just change it to a u32 for now.

Based on patch by Rusty.

Suggested-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>

4 files changed, 12 insertions, 33 deletions

diff --git a/tools/virtio/linux/virtio.h b/tools/virtio/linux/virtio.h
index 5a2d1f0f6bc7..72bff70bfeeb 100644
--- a/tools/virtio/linux/virtio.h
+++ b/tools/virtio/linux/virtio.h
@@ -6,31 +6,11 @@
 /* TODO: empty stubs for now. Broken but enough for virtio_ring.c */
 #define list_add_tail(a, b) do {} while (0)
 #define list_del(a) do {} while (0)
-
-#define BIT_WORD(nr)            ((nr) / BITS_PER_LONG)
-#define BITS_PER_BYTE           8
-#define BITS_PER_LONG (sizeof(long) * BITS_PER_BYTE)
-#define BIT_MASK(nr)            (1UL << ((nr) % BITS_PER_LONG))
-
-/* TODO: Not atomic as it should be:
- * we don't use this for anything important. */
-static inline void clear_bit(int nr, volatile unsigned long *addr)
-{
-        unsigned long mask = BIT_MASK(nr);
-        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
-
-        *p &= ~mask;
-}
-
-static inline int test_bit(int nr, const volatile unsigned long *addr)
-{
-        return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
-}
 /* end of stubs */
 
 struct virtio_device {
         void *dev;
-        unsigned long features[1];
+        u32 features;
 };
 
 struct virtqueue {
diff --git a/tools/virtio/linux/virtio_config.h b/tools/virtio/linux/virtio_config.h
index 5049967f99f7..83b27e8e9d72 100644
--- a/tools/virtio/linux/virtio_config.h
+++ b/tools/virtio/linux/virtio_config.h
@@ -2,5 +2,5 @@
 #define VIRTIO_TRANSPORT_F_END          32
 
 #define virtio_has_feature(dev, feature) \
-        test_bit((feature), (dev)->features)
+        (__virtio_test_bit((dev), feature))
 
diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c
index 00ea679b3826..db3437c641a6 100644
--- a/tools/virtio/virtio_test.c
+++ b/tools/virtio/virtio_test.c
@@ -60,7 +60,7 @@ void vhost_vq_setup(struct vdev_info *dev, struct vq_info *info)
 {
         struct vhost_vring_state state = { .index = info->idx };
         struct vhost_vring_file file = { .index = info->idx };
-        unsigned long long features = dev->vdev.features[0];
+        unsigned long long features = dev->vdev.features;
         struct vhost_vring_addr addr = {
                 .index = info->idx,
                 .desc_user_addr = (uint64_t)(unsigned long)info->vring.desc,
@@ -113,8 +113,7 @@ static void vdev_info_init(struct vdev_info* dev, unsigned long long features)
 {
         int r;
         memset(dev, 0, sizeof *dev);
-        dev->vdev.features[0] = features;
-        dev->vdev.features[1] = features >> 32;
+        dev->vdev.features = features;
         dev->buf_size = 1024;
         dev->buf = malloc(dev->buf_size);
         assert(dev->buf);
diff --git a/tools/virtio/vringh_test.c b/tools/virtio/vringh_test.c
index 14a4f4cab5b9..9d4b1bca54be 100644
--- a/tools/virtio/vringh_test.c
+++ b/tools/virtio/vringh_test.c
@@ -304,7 +304,7 @@ static int parallel_test(unsigned long features,
                 close(to_guest[1]);
                 close(to_host[0]);
 
-                gvdev.vdev.features[0] = features;
+                gvdev.vdev.features = features;
                 gvdev.to_host_fd = to_host[1];
                 gvdev.notifies = 0;
 
@@ -449,13 +449,13 @@ int main(int argc, char *argv[])
         bool fast_vringh = false, parallel = false;
 
         getrange = getrange_iov;
-        vdev.features[0] = 0;
+        vdev.features = 0;
 
         while (argv[1]) {
                 if (strcmp(argv[1], "--indirect") == 0)
-                        vdev.features[0] |= (1 << VIRTIO_RING_F_INDIRECT_DESC);
+                        __virtio_set_bit(&vdev, VIRTIO_RING_F_INDIRECT_DESC);
                 else if (strcmp(argv[1], "--eventidx") == 0)
-                        vdev.features[0] |= (1 << VIRTIO_RING_F_EVENT_IDX);
+                        __virtio_set_bit(&vdev, VIRTIO_RING_F_EVENT_IDX);
                 else if (strcmp(argv[1], "--slow-range") == 0)
                         getrange = getrange_slow;
                 else if (strcmp(argv[1], "--fast-vringh") == 0)
@@ -468,7 +468,7 @@ int main(int argc, char *argv[])
         }
 
         if (parallel)
-                return parallel_test(vdev.features[0], getrange, fast_vringh);
+                return parallel_test(vdev.features, getrange, fast_vringh);
 
         if (posix_memalign(&__user_addr_min, PAGE_SIZE, USER_MEM) != 0)
                 abort();
@@ -483,7 +483,7 @@ int main(int argc, char *argv[])
 
         /* Set up host side. */
         vring_init(&vrh.vring, RINGSIZE, __user_addr_min, ALIGN);
-        vringh_init_user(&vrh, vdev.features[0], RINGSIZE, true,
+        vringh_init_user(&vrh, vdev.features, RINGSIZE, true,
                          vrh.vring.desc, vrh.vring.avail, vrh.vring.used);
 
         /* No descriptor to get yet... */
@@ -652,13 +652,13 @@ int main(int argc, char *argv[])
         }
 
         /* Test weird (but legal!) indirect. */
-        if (vdev.features[0] & (1 << VIRTIO_RING_F_INDIRECT_DESC)) {
+        if (__virtio_test_bit(&vdev, VIRTIO_RING_F_INDIRECT_DESC)) {
                 char *data = __user_addr_max - USER_MEM/4;
                 struct vring_desc *d = __user_addr_max - USER_MEM/2;
                 struct vring vring;
 
                 /* Force creation of direct, which we modify. */
-                vdev.features[0] &= ~(1 << VIRTIO_RING_F_INDIRECT_DESC);
+                __virtio_clear_bit(&vdev, VIRTIO_RING_F_INDIRECT_DESC);
                 vq = vring_new_virtqueue(0, RINGSIZE, ALIGN, &vdev, true,
                                          __user_addr_min,
                                          never_notify_host,