The virtio specifications allows for up to 128 bits for the
device features. Soon we are going to use some of the 'extended'
bits features (above 64) for the virtio_net driver.

Extend the virtio pci modern driver to support configuring the full
virtio features range, replacing the unrolled loops reading and
writing the features space with explicit one bounded to the actual
features space size in word and implementing the get_extended_features
callback.

Note that in vp_finalize_features() we only need to cache the lower
64 features bits, to process the transport features.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v3 -> v4:
  - dropped unneeded check in vp_modern_get_features()

v2 -> v3:
  - virtio_features_t -> u64 *

v1 -> v2:
  - use get_extended_features
---
 drivers/virtio/virtio_pci_modern.c     | 10 ++--
 drivers/virtio/virtio_pci_modern_dev.c | 69 +++++++++++++++-----------
 include/linux/virtio_pci_modern.h      | 43 ++++++++++++++--
 3 files changed, 84 insertions(+), 38 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 7182f43ed055..dd0e65f71d41 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c

@@ -22,11 +22,11 @@

 #define VIRTIO_AVQ_SGS_MAX     4

-static u64 vp_get_features(struct virtio_device *vdev)
+static void vp_get_features(struct virtio_device *vdev, u64 *features)
 {
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);

-       return vp_modern_get_features(&vp_dev->mdev);
+       vp_modern_get_extended_features(&vp_dev->mdev, features);
 }

 static int vp_avq_index(struct virtio_device *vdev, u16 *index, u16 *num)

@@ -437,7 +437,7 @@ static int vp_finalize_features(struct virtio_device *vdev)
        if (vp_check_common_size(vdev))
                return -EINVAL;

-       vp_modern_set_features(&vp_dev->mdev, vdev->features);
+       vp_modern_set_extended_features(&vp_dev->mdev, vdev->features_array);

        return 0;
 }

@@ -1234,7 +1234,7 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
        .find_vqs       = vp_modern_find_vqs,
        .del_vqs        = vp_del_vqs,
        .synchronize_cbs = vp_synchronize_vectors,
-       .get_features   = vp_get_features,
+       .get_extended_features = vp_get_features,
        .finalize_features = vp_finalize_features,
        .bus_name       = vp_bus_name,
        .set_vq_affinity = vp_set_vq_affinity,

@@ -1254,7 +1254,7 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
        .find_vqs       = vp_modern_find_vqs,
        .del_vqs        = vp_del_vqs,
        .synchronize_cbs = vp_synchronize_vectors,
-       .get_features   = vp_get_features,
+       .get_extended_features = vp_get_features,
        .finalize_features = vp_finalize_features,
        .bus_name       = vp_bus_name,
        .set_vq_affinity = vp_set_vq_affinity,

diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index 0d3dbfaf4b23..d665f8f73ea8 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c

@@ -388,63 +388,74 @@ void vp_modern_remove(struct virtio_pci_modern_device *mdev)
 EXPORT_SYMBOL_GPL(vp_modern_remove);

 /*
- * vp_modern_get_features - get features from device
+ * vp_modern_get_extended_features - get features from device
  * @mdev: the modern virtio-pci device
+ * @features: the features array to be filled
  *
- * Returns the features read from the device
+ * Fill the specified features array with the features read from the device
  */
-u64 vp_modern_get_features(struct virtio_pci_modern_device *mdev)
+void vp_modern_get_extended_features(struct virtio_pci_modern_device *mdev,
+                                    u64 *features)
 {
        struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
+       int i;

-       u64 features;
+       virtio_features_zero(features);
+       for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+               u64 cur;

-       vp_iowrite32(0, &cfg->device_feature_select);
-       features = vp_ioread32(&cfg->device_feature);
-       vp_iowrite32(1, &cfg->device_feature_select);
-       features |= ((u64)vp_ioread32(&cfg->device_feature) << 32);
-
-       return features;
+               vp_iowrite32(i, &cfg->device_feature_select);
+               cur = vp_ioread32(&cfg->device_feature);
+               features[i >> 1] |= cur << (32 * (i & 1));