Re: [PATCH] vdpa/mlx5: Avoid warnings about shifts on 32-bit platforms

From: Nathan Chancellor
Date: Fri Aug 21 2020 - 19:20:42 EST

On Fri, Aug 21, 2020 at 04:13:19PM -0700, Randy Dunlap wrote:
> On 8/21/20 3:50 PM, Nathan Chancellor wrote:
> > Clang warns several times when building for 32-bit ARM along the lines
> > of:
> >
> > drivers/vdpa/mlx5/net/mlx5_vnet.c:1462:31: warning: shift count >= width
> > of type [-Wshift-count-overflow]
> > ndev->mvdev.mlx_features |= BIT(VIRTIO_F_VERSION_1);
> > ^~~~~~~~~~~~~~~~~~~~~~~
> >
> > This is related to the BIT macro, which uses an unsigned long literal,
> > which is 32-bit on ARM so having a shift equal to or larger than 32 will
> > cause this warning, such as the above, where VIRTIO_F_VERSION_1 is 32.
> > To avoid this, use BIT_ULL, which will be an unsigned long long. This
> > matches the size of the features field throughout this driver, which is
> > u64 so there should be no functional change.
> >
> > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1140
> > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
>
> Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> on 2020-AUG-10 for i386:
> https://lore.kernel.org/linux-next/5a7a0e6d-842a-78f6-aeac-c5b4c27b7186@xxxxxxxxxxxxx/
> :(

Sorry, I saw this in my own build tests and was not aware of the
previous report since I have not really been paying attention to
the mailing lists as of late :(

Should I need to do a v2, I will be sure to include that tag; otherwise,
it would be great if it could be picked up along with the below.

> Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> # build-tested

Thank you for testing!

> Thanks.
>
> > ---
> > drivers/vdpa/mlx5/net/mlx5_vnet.c | 50 +++++++++++++++----------------
> > 1 file changed, 25 insertions(+), 25 deletions(-)
> >
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 9df69d5efe8c..70676a6d1691 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -16,19 +16,19 @@
> > #define to_mvdev(__vdev) container_of((__vdev), struct mlx5_vdpa_dev, vdev)
> >
> > #define VALID_FEATURES_MASK \
> > - (BIT(VIRTIO_NET_F_CSUM) | BIT(VIRTIO_NET_F_GUEST_CSUM) | \
> > - BIT(VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) | BIT(VIRTIO_NET_F_MTU) | BIT(VIRTIO_NET_F_MAC) | \
> > - BIT(VIRTIO_NET_F_GUEST_TSO4) | BIT(VIRTIO_NET_F_GUEST_TSO6) | \
> > - BIT(VIRTIO_NET_F_GUEST_ECN) | BIT(VIRTIO_NET_F_GUEST_UFO) | BIT(VIRTIO_NET_F_HOST_TSO4) | \
> > - BIT(VIRTIO_NET_F_HOST_TSO6) | BIT(VIRTIO_NET_F_HOST_ECN) | BIT(VIRTIO_NET_F_HOST_UFO) | \
> > - BIT(VIRTIO_NET_F_MRG_RXBUF) | BIT(VIRTIO_NET_F_STATUS) | BIT(VIRTIO_NET_F_CTRL_VQ) | \
> > - BIT(VIRTIO_NET_F_CTRL_RX) | BIT(VIRTIO_NET_F_CTRL_VLAN) | \
> > - BIT(VIRTIO_NET_F_CTRL_RX_EXTRA) | BIT(VIRTIO_NET_F_GUEST_ANNOUNCE) | \
> > - BIT(VIRTIO_NET_F_MQ) | BIT(VIRTIO_NET_F_CTRL_MAC_ADDR) | BIT(VIRTIO_NET_F_HASH_REPORT) | \
> > - BIT(VIRTIO_NET_F_RSS) | BIT(VIRTIO_NET_F_RSC_EXT) | BIT(VIRTIO_NET_F_STANDBY) | \
> > - BIT(VIRTIO_NET_F_SPEED_DUPLEX) | BIT(VIRTIO_F_NOTIFY_ON_EMPTY) | \
> > - BIT(VIRTIO_F_ANY_LAYOUT) | BIT(VIRTIO_F_VERSION_1) | BIT(VIRTIO_F_ACCESS_PLATFORM) | \
> > - BIT(VIRTIO_F_RING_PACKED) | BIT(VIRTIO_F_ORDER_PLATFORM) | BIT(VIRTIO_F_SR_IOV))
> > + (BIT_ULL(VIRTIO_NET_F_CSUM) | BIT_ULL(VIRTIO_NET_F_GUEST_CSUM) | \
> > + BIT_ULL(VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) | BIT_ULL(VIRTIO_NET_F_MTU) | BIT_ULL(VIRTIO_NET_F_MAC) | \
> > + BIT_ULL(VIRTIO_NET_F_GUEST_TSO4) | BIT_ULL(VIRTIO_NET_F_GUEST_TSO6) | \
> > + BIT_ULL(VIRTIO_NET_F_GUEST_ECN) | BIT_ULL(VIRTIO_NET_F_GUEST_UFO) | BIT_ULL(VIRTIO_NET_F_HOST_TSO4) | \
> > + BIT_ULL(VIRTIO_NET_F_HOST_TSO6) | BIT_ULL(VIRTIO_NET_F_HOST_ECN) | BIT_ULL(VIRTIO_NET_F_HOST_UFO) | \
> > + BIT_ULL(VIRTIO_NET_F_MRG_RXBUF) | BIT_ULL(VIRTIO_NET_F_STATUS) | BIT_ULL(VIRTIO_NET_F_CTRL_VQ) | \
> > + BIT_ULL(VIRTIO_NET_F_CTRL_RX) | BIT_ULL(VIRTIO_NET_F_CTRL_VLAN) | \
> > + BIT_ULL(VIRTIO_NET_F_CTRL_RX_EXTRA) | BIT_ULL(VIRTIO_NET_F_GUEST_ANNOUNCE) | \
> > + BIT_ULL(VIRTIO_NET_F_MQ) | BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR) | BIT_ULL(VIRTIO_NET_F_HASH_REPORT) | \
> > + BIT_ULL(VIRTIO_NET_F_RSS) | BIT_ULL(VIRTIO_NET_F_RSC_EXT) | BIT_ULL(VIRTIO_NET_F_STANDBY) | \
> > + BIT_ULL(VIRTIO_NET_F_SPEED_DUPLEX) | BIT_ULL(VIRTIO_F_NOTIFY_ON_EMPTY) | \
> > + BIT_ULL(VIRTIO_F_ANY_LAYOUT) | BIT_ULL(VIRTIO_F_VERSION_1) | BIT_ULL(VIRTIO_F_ACCESS_PLATFORM) | \
> > + BIT_ULL(VIRTIO_F_RING_PACKED) | BIT_ULL(VIRTIO_F_ORDER_PLATFORM) | BIT_ULL(VIRTIO_F_SR_IOV))
> >
> > #define VALID_STATUS_MASK \
> > (VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK | \
> > @@ -149,7 +149,7 @@ static bool mlx5_vdpa_debug;
> >
> > #define MLX5_LOG_VIO_FLAG(_feature) \
> > do { \
> > - if (features & BIT(_feature)) \
> > + if (features & BIT_ULL(_feature)) \
> > mlx5_vdpa_info(mvdev, "%s\n", #_feature); \
> > } while (0)
> >
> > @@ -750,10 +750,10 @@ static bool vq_is_tx(u16 idx)
> >
> > static u16 get_features_12_3(u64 features)
> > {
> > - return (!!(features & BIT(VIRTIO_NET_F_HOST_TSO4)) << 9) |
> > - (!!(features & BIT(VIRTIO_NET_F_HOST_TSO6)) << 8) |
> > - (!!(features & BIT(VIRTIO_NET_F_CSUM)) << 7) |
> > - (!!(features & BIT(VIRTIO_NET_F_GUEST_CSUM)) << 6);
> > + return (!!(features & BIT_ULL(VIRTIO_NET_F_HOST_TSO4)) << 9) |
> > + (!!(features & BIT_ULL(VIRTIO_NET_F_HOST_TSO6)) << 8) |
> > + (!!(features & BIT_ULL(VIRTIO_NET_F_CSUM)) << 7) |
> > + (!!(features & BIT_ULL(VIRTIO_NET_F_GUEST_CSUM)) << 6);
> > }
> >
> > static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
> > @@ -1439,13 +1439,13 @@ static u64 mlx_to_vritio_features(u16 dev_features)
> > u64 result = 0;
> >
> > if (dev_features & MLX5_VIRTIO_NET_F_GUEST_CSUM)
> > - result |= BIT(VIRTIO_NET_F_GUEST_CSUM);
> > + result |= BIT_ULL(VIRTIO_NET_F_GUEST_CSUM);
> > if (dev_features & MLX5_VIRTIO_NET_F_CSUM)
> > - result |= BIT(VIRTIO_NET_F_CSUM);
> > + result |= BIT_ULL(VIRTIO_NET_F_CSUM);
> > if (dev_features & MLX5_VIRTIO_NET_F_HOST_TSO6)
> > - result |= BIT(VIRTIO_NET_F_HOST_TSO6);
> > + result |= BIT_ULL(VIRTIO_NET_F_HOST_TSO6);
> > if (dev_features & MLX5_VIRTIO_NET_F_HOST_TSO4)
> > - result |= BIT(VIRTIO_NET_F_HOST_TSO4);
> > + result |= BIT_ULL(VIRTIO_NET_F_HOST_TSO4);
> >
> > return result;
> > }
> > @@ -1459,15 +1459,15 @@ static u64 mlx5_vdpa_get_features(struct vdpa_device *vdev)
> > dev_features = MLX5_CAP_DEV_VDPA_EMULATION(mvdev->mdev, device_features_bits_mask);
> > ndev->mvdev.mlx_features = mlx_to_vritio_features(dev_features);
> > if (MLX5_CAP_DEV_VDPA_EMULATION(mvdev->mdev, virtio_version_1_0))
> > - ndev->mvdev.mlx_features |= BIT(VIRTIO_F_VERSION_1);
> > - ndev->mvdev.mlx_features |= BIT(VIRTIO_F_ACCESS_PLATFORM);
> > + ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_F_VERSION_1);
> > + ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_F_ACCESS_PLATFORM);
> > print_features(mvdev, ndev->mvdev.mlx_features, false);
> > return ndev->mvdev.mlx_features;
> > }
> >
> > static int verify_min_features(struct mlx5_vdpa_dev *mvdev, u64 features)
> > {
> > - if (!(features & BIT(VIRTIO_F_ACCESS_PLATFORM)))
> > + if (!(features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
> > return -EOPNOTSUPP;
> >
> > return 0;
> >
> > base-commit: 8a7c3213db068135e816a6a517157de6443290d6
> >
>
>
> --
> ~Randy
>
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