netdev - [PATCH net-next 2/8] virtio_pci_modern: allow setting configuring extended features

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Message-ID: <f85bc2d08dfd1a686b1cd102977f615aa07b3190.1747822866.git.pabeni@redhat.com>
Date: Wed, 21 May 2025 12:32:36 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	Jason Wang <jasowang@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>
Subject: [PATCH net-next 2/8] virtio_pci_modern: allow setting configuring extended features

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.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 drivers/virtio/virtio_pci_modern_dev.c | 39 +++++++++++++++++---------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index 1d34655f6b658..e3025b6fa8540 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c
@@ -396,12 +396,16 @@ EXPORT_SYMBOL_GPL(vp_modern_remove);
 virtio_features_t vp_modern_get_features(struct virtio_pci_modern_device *mdev)
 {
 	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
-	virtio_features_t features;
+	virtio_features_t features = 0;
+	int i;
 
-	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);
+	for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+		virtio_features_t cur;
+
+		vp_iowrite32(i, &cfg->device_feature_select);
+		cur = vp_ioread32(&cfg->device_feature);
+		features |= cur << (32 * i);
+	}
 
 	return features;
 }
@@ -417,12 +421,16 @@ virtio_features_t
 vp_modern_get_driver_features(struct virtio_pci_modern_device *mdev)
 {
 	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
-	virtio_features_t features;
+	virtio_features_t features = 0;
+	int i;
+
+	for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+		virtio_features_t cur;
 
-	vp_iowrite32(0, &cfg->guest_feature_select);
-	features = vp_ioread32(&cfg->guest_feature);
-	vp_iowrite32(1, &cfg->guest_feature_select);
-	features |= ((u64)vp_ioread32(&cfg->guest_feature) << 32);
+		vp_iowrite32(i, &cfg->guest_feature_select);
+		cur = vp_ioread32(&cfg->guest_feature);
+		features |= cur << (32 * i);
+	}
 
 	return features;
 }
@@ -437,11 +445,14 @@ void vp_modern_set_features(struct virtio_pci_modern_device *mdev,
 			    virtio_features_t features)
 {
 	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
+	int i;
+
+	for (i = 0; i < VIRTIO_FEATURES_WORDS; i++) {
+		u32 cur = features >> (32 * i);
 
-	vp_iowrite32(0, &cfg->guest_feature_select);
-	vp_iowrite32((u32)features, &cfg->guest_feature);
-	vp_iowrite32(1, &cfg->guest_feature_select);
-	vp_iowrite32(features >> 32, &cfg->guest_feature);
+		vp_iowrite32(i, &cfg->guest_feature_select);
+		vp_iowrite32(cur, &cfg->guest_feature);
+	}
 }
 EXPORT_SYMBOL_GPL(vp_modern_set_features);
 
-- 
2.49.0