On 6/18/25 4:27 AM, Jason Wang wrote:

On Wed, Jun 18, 2025 at 12:12 AM Paolo Abeni [off-list ref] wrote:

quoted

/*
- * 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));

Nit: why not simply cast features to u32 * then everything is simplified.

I can be (and usually I am) low on coffee, but I think that will work
only for BE architectures.

/P