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>

16 files changed, 42 insertions, 74 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index cf7a561fad7c..8d00aa7f60f0 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -355,7 +355,7 @@ static inline bool use_multiport(struct ports_device *portdev)
          */
         if (!portdev->vdev)
                 return 0;
-        return portdev->vdev->features[0] & (1 << VIRTIO_CONSOLE_F_MULTIPORT);
+        return __virtio_test_bit(portdev->vdev, VIRTIO_CONSOLE_F_MULTIPORT);
 }
 
 static DEFINE_SPINLOCK(dma_bufs_lock);
diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c
index d0a1d8a45c81..97aeb7dce5fc 100644
--- a/drivers/lguest/lguest_device.c
+++ b/drivers/lguest/lguest_device.c
@@ -137,14 +137,14 @@ static void lg_finalize_features(struct virtio_device *vdev)
         vring_transport_features(vdev);
 
         /*
-         * The vdev->feature array is a Linux bitmask: this isn't the same as a
-         * the simple array of bits used by lguest devices for features.  So we
-         * do this slow, manual conversion which is completely general.
+         * Since lguest is currently x86-only, we're little-endian.  That
+         * means we could just memcpy.  But it's not time critical, and in
+         * case someone copies this code, we do it the slow, obvious way.
          */
         memset(out_features, 0, desc->feature_len);
         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
         for (i = 0; i < bits; i++) {
-                if (test_bit(i, vdev->features))
+                if (__virtio_test_bit(vdev, i))
                         out_features[i / 8] |= (1 << (i % 8));
         }
 
diff --git a/drivers/misc/mic/card/mic_virtio.c b/drivers/misc/mic/card/mic_virtio.c
index e64794730e21..4f070ad1875c 100644
--- a/drivers/misc/mic/card/mic_virtio.c
+++ b/drivers/misc/mic/card/mic_virtio.c
@@ -101,7 +101,7 @@ static void mic_finalize_features(struct virtio_device *vdev)
         bits = min_t(unsigned, feature_len,
                 sizeof(vdev->features)) * 8;
         for (i = 0; i < bits; i++) {
-                if (test_bit(i, vdev->features))
+                if (__virtio_test_bit(vdev, i))
                         iowrite8(ioread8(&out_features[i / 8]) | (1 << (i % 8)),
                                  &out_features[i / 8]);
         }
diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
index a34b50690b4e..dafaf38dac0a 100644
--- a/drivers/remoteproc/remoteproc_virtio.c
+++ b/drivers/remoteproc/remoteproc_virtio.c
@@ -231,7 +231,7 @@ static void rproc_virtio_finalize_features(struct virtio_device *vdev)
          * Remember the finalized features of our vdev, and provide it
          * to the remote processor once it is powered on.
          */
-        rsc->gfeatures = vdev->features[0];
+        rsc->gfeatures = vdev->features;
 }
 
 static void rproc_virtio_get(struct virtio_device *vdev, unsigned offset,
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 643129070c51..fcd312d0c018 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -106,7 +106,7 @@ static void kvm_finalize_features(struct virtio_device *vdev)
         memset(out_features, 0, desc->feature_len);
         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
         for (i = 0; i < bits; i++) {
-                if (test_bit(i, vdev->features))
+                if (__virtio_test_bit(vdev, i))
                         out_features[i / 8] |= (1 << (i % 8));
         }
 }
diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index bda52f18e967..1dbee95838fe 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -701,7 +701,6 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
 {
         struct virtio_ccw_device *vcdev = to_vc_device(vdev);
         struct virtio_feature_desc *features;
-        int i;
         struct ccw1 *ccw;
 
         ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
@@ -715,19 +714,15 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
         /* Give virtio_ring a chance to accept features. */
         vring_transport_features(vdev);
 
-        for (i = 0; i < sizeof(*vdev->features) / sizeof(features->features);
-             i++) {
-                int highbits = i % 2 ? 32 : 0;
-                features->index = i;
-                features->features = cpu_to_le32(vdev->features[i / 2]
-                                                 >> highbits);
-                /* Write the feature bits to the host. */
-                ccw->cmd_code = CCW_CMD_WRITE_FEAT;
-                ccw->flags = 0;
-                ccw->count = sizeof(*features);
-                ccw->cda = (__u32)(unsigned long)features;
-                ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
-        }
+        features->index = 0;
+        features->features = cpu_to_le32(vdev->features);
+        /* Write the feature bits to the host. */
+        ccw->cmd_code = CCW_CMD_WRITE_FEAT;
+        ccw->flags = 0;
+        ccw->count = sizeof(*features);
+        ccw->cda = (__u32)(unsigned long)features;
+        ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
+
 out_free:
         kfree(features);
         kfree(ccw);
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index df598dd8c5c8..2b9aafb4d679 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -49,9 +49,9 @@ 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 < ARRAY_SIZE(dev->features)*BITS_PER_LONG; i++)
+        for (i = 0; i < sizeof(dev->features)*8; i++)
                 len += sprintf(buf+len, "%c",
-                               test_bit(i, dev->features) ? '1' : '0');
+                               __virtio_test_bit(dev, i) ? '1' : '0');
         len += sprintf(buf+len, "\n");
         return len;
 }
@@ -168,18 +168,18 @@ static int virtio_dev_probe(struct device *_d)
         device_features = dev->config->get_features(dev);
 
         /* Features supported by both device and driver into dev->features. */
-        memset(dev->features, 0, sizeof(dev->features));
+        dev->features = 0;
         for (i = 0; i < drv->feature_table_size; i++) {
                 unsigned int f = drv->feature_table[i];
                 BUG_ON(f >= 32);
                 if (device_features & (1 << f))
-                        set_bit(f, dev->features);
+                        __virtio_set_bit(dev, f);
         }
 
         /* Transport features always preserved to pass to finalize_features. */
         for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)
                 if (device_features & (1 << i))
-                        set_bit(i, dev->features);
+                        __virtio_set_bit(dev, i);
 
         dev->config->finalize_features(dev);
 
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index ef9a1650bb80..eb5b0e2b434a 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -155,16 +155,12 @@ static u32 vm_get_features(struct virtio_device *vdev)
 static void vm_finalize_features(struct virtio_device *vdev)
 {
         struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
-        int i;
 
         /* Give virtio_ring a chance to accept features. */
         vring_transport_features(vdev);
 
-        for (i = 0; i < ARRAY_SIZE(vdev->features); i++) {
-                writel(i, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
-                writel(vdev->features[i],
-                                vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
-        }
+        writel(0, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
+        writel(vdev->features, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
 }
 
 static void vm_get(struct virtio_device *vdev, unsigned offset,
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index d34ebfa604f3..4e112c158488 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -120,8 +120,7 @@ static void vp_finalize_features(struct virtio_device *vdev)
         vring_transport_features(vdev);
 
         /* We only support 32 feature bits. */
-        BUILD_BUG_ON(ARRAY_SIZE(vdev->features) != 1);
-        iowrite32(vdev->features[0], vp_dev->ioaddr+VIRTIO_PCI_GUEST_FEATURES);
+        iowrite32(vdev->features, vp_dev->ioaddr + VIRTIO_PCI_GUEST_FEATURES);
 }
 
 /* virtio config->get() implementation */
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 3b1f89b6e743..839247cd8263 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -781,7 +781,7 @@ void vring_transport_features(struct virtio_device *vdev)
                         break;
                 default:
                         /* We don't understand this bit. */
-                        clear_bit(i, vdev->features);
+                        __virtio_clear_bit(vdev, i);
                 }
         }
 }
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 65261a7244fc..7828a7f47c2c 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -101,8 +101,7 @@ struct virtio_device {
         const struct virtio_config_ops *config;
         const struct vringh_config_ops *vringh_config;
         struct list_head vqs;
-        /* Note that this is a Linux set_bit-style bitmap. */
-        unsigned long features[1];
+        u32 features;
         void *priv;
 };
 
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index d8e28a2a5738..ffc2ae04879c 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -92,7 +92,7 @@ static inline bool __virtio_test_bit(const struct virtio_device *vdev,
         else
                 BUG_ON(fbit >= 32);
 
-        return test_bit(fbit, vdev->features);
+        return vdev->features & BIT(fbit);
 }
 
 /**
@@ -109,7 +109,7 @@ static inline void __virtio_set_bit(struct virtio_device *vdev,
         else
                 BUG_ON(fbit >= 32);
 
-        set_bit(fbit, vdev->features);
+        vdev->features |= BIT(fbit);
 }
 
 /**
@@ -126,7 +126,7 @@ static inline void __virtio_clear_bit(struct virtio_device *vdev,
         else
                 BUG_ON(fbit >= 32);
 
-        clear_bit(fbit, vdev->features);
+        vdev->features &= ~BIT(fbit);
 }
 
 /**
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,