[PATCH 3/3] vhost: use checked versions of VIRTIO_BIT
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2025-10-09 11:24:23
Also in:
kvm, lkml, virtualization
Subsystem:
the rest, virtio core, virtio host (vhost) · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang
This adds compile-time checked versions of VIRTIO_BIT that set bits in low and high qword, respectively. Will prevent confusion when people set bits in the wrong qword. Cc: "Paolo Abeni" <pabeni@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- drivers/vhost/net.c | 4 ++-- include/linux/virtio_features.h | 9 +++++++++ 2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 43d51fb1f8ea..8b98e1a8baaa 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c@@ -76,8 +76,8 @@ static const u64 vhost_net_features[VIRTIO_FEATURES_QWORDS] = { (1ULL << VIRTIO_F_ACCESS_PLATFORM) | (1ULL << VIRTIO_F_RING_RESET) | (1ULL << VIRTIO_F_IN_ORDER), - VIRTIO_BIT(VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) | - VIRTIO_BIT(VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO), + VIRTIO_BIT_HI(VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) | + VIRTIO_BIT_HI(VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO), }; enum {
diff --git a/include/linux/virtio_features.h b/include/linux/virtio_features.h
index f41acb035af9..466f7d8ed5ba 100644
--- a/include/linux/virtio_features.h
+++ b/include/linux/virtio_features.h@@ -9,6 +9,15 @@ #define VIRTIO_FEATURES_DWORDS (VIRTIO_FEATURES_QWORDS * 2) #define VIRTIO_BIT(b) BIT_ULL((b) & 0x3f) #define VIRTIO_QWORD(b) ((b) >> 6) + +/* Get a given feature bit in a given qword. */ +#define VIRTIO_BIT_QWORD(bit, qword) \ + (BUILD_BUG_ON_ZERO(const_true(VIRTIO_QWORD(bit) != (qword))) + \ + BIT_ULL((bit) - 64 * (qword))) + +#define VIRTIO_BIT_LO(b) VIRTIO_BIT_QWORD(b, 0) +#define VIRTIO_BIT_HI(b) VIRTIO_BIT_QWORD(b, 1) + #define VIRTIO_DECLARE_FEATURES(name) \ union { \ u64 name; \
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MST