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From: Alexander Graf <graf@amazon.com>
To: "Michael S. Tsirkin" <mst@redhat.com>, Jason Wang <jasowangio@gmail.com>
Cc: nh-open-source@amazon.com,
	"Xuan Zhuo" <xuanzhuo@linux.alibaba.com>,
	"Eugenio Pérez" <eperezma@redhat.com>,
	"Yishai Hadas" <yishaih@nvidia.com>,
	"Alex Williamson" <alex@shazbot.org>,
	"Feng Liu" <feliu@nvidia.com>, "Jiri Pirko" <jiri@resnulli.us>,
	virtualization@lists.linux.dev, linux-kernel@vger.kernel.org,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>
Subject: [PATCH v2 03/12] vdpa: drop the VIRTIO_DEVICE_F_MASK example value
Date: Tue, 18 Aug 2026 21:14:16 +0000	[thread overview]
Message-ID: <20260818211425.91009-4-graf@amazon.com> (raw)
In-Reply-To: <20260818211425.91009-1-graf@amazon.com>

The comment above VIRTIO_DEVICE_F_MASK spells the mask out by hand as
0xfffffc000fffffff, which was correct while VIRTIO_TRANSPORT_F_END was
41. The bound is 42 now, so the macro expands to 0xfffff8000fffffff and
whoever reads the comment to check a feature mask against it gets the
wrong boundary between transport and per-device bits.

Correcting the number would leave a comment that has to be updated by
hand every time the bound moves, and we already missed it once. Drop the
expansion instead. The macro derives its value from the bound and needs
no change.

Fixes: 838bebb4c926 ("virtio: Define feature bit for administration virtqueue")
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Assisted-by: Kiro:claude-opus-5 checkpatch sparse
Signed-off-by: Alexander Graf <graf@amazon.com>
---
 drivers/vdpa/vdpa.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 47c6c3d23f5c..395ca549573a 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -548,10 +548,9 @@ vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
 
 /*
  * Bitmask for all per-device features: feature bits VIRTIO_TRANSPORT_F_START
- * through VIRTIO_TRANSPORT_F_END are unset, i.e. 0xfffffc000fffffff for
- * all 64bit features. If the features are extended beyond 64 bits, or new
- * "holes" are reserved for other type of features than per-device, this
- * macro would have to be updated.
+ * through VIRTIO_TRANSPORT_F_END are unset. If the features are extended
+ * beyond 64 bits, or new "holes" are reserved for other type of features
+ * than per-device, this macro would have to be updated.
  */
 #define VIRTIO_DEVICE_F_MASK (~0ULL << (VIRTIO_TRANSPORT_F_END + 1) | \
 			      ((1ULL << VIRTIO_TRANSPORT_F_START) - 1))

  parent reply	other threads:[~2026-08-18 21:15 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-18 21:14 [PATCH v2 00/12] virtio: support devices that own their virtqueue memory Alexander Graf
2026-08-18 21:14 ` [PATCH v2 01/12] virtio_ring: remove the unused map sync API Alexander Graf
2026-08-18 21:14 ` [PATCH v2 02/12] virtio: drop the sync operations from virtio_map_ops Alexander Graf
2026-08-18 21:14 ` Alexander Graf [this message]
2026-08-18 21:14 ` [PATCH v2 04/12] virtio_ring: return -ENOMEM when a packed ring mapping fails Alexander Graf
2026-08-18 21:14 ` [PATCH v2 05/12] virtio: add the VIRTIO_F_DMB feature bit Alexander Graf
2026-08-18 21:14 ` [PATCH v2 06/12] virtio_pci: read the device memory buffer registers Alexander Graf
2026-08-18 21:14 ` [PATCH v2 07/12] virtio_pci: create virtqueues with the device's mapping token Alexander Graf
2026-08-18 21:14 ` [PATCH v2 08/12] virtio: add a device memory buffer region allocator Alexander Graf
2026-08-18 21:14 ` [PATCH v2 09/12] virtio: locate the device memory buffer after feature negotiation Alexander Graf
2026-08-18 21:14 ` [PATCH v2 10/12] virtio: treat VIRTIO_F_DMB as implying VIRTIO_F_ACCESS_PLATFORM Alexander Graf
2026-08-18 21:14 ` [PATCH v2 11/12] virtio_pci: support VIRTIO_F_DMB Alexander Graf
2026-08-18 21:40   ` sashiko-bot
2026-08-18 21:14 ` [PATCH v2 12/12] virtio: expose device memory buffer occupancy over debugfs Alexander Graf

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