[PATCH 04/11] net/mlx5: Add ONCE and MMIO accessor variants to mlx5_ifc_macros.h

Jason Gunthorpe
2026-05-01T00:08:45Z

Add MLX5_GET_ONCE / MLX5_SET_ONCE which include READ_ONCE/WRITE_ONCE
semantics for touching ownership bits that hardware may read or write
at any time. The kernel driver doesn't use the IFC struct for these
ownership bits, but the VFIO driver will and needs these helpers.

Add MLX5_GET_MMIO / MLX5_SET_MMIO for accessing the init seg using
the IFC offsets. They embed a readl/writel using the IFC struct to
generate the addressing.

Add MLX5_ARRAY_GET64(), the missing counterpart to
MLX5_ARRAY_SET64().

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
include/linux/mlx5/mlx5_ifc_macros.h | 52 ++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)

diff --git a/include/linux/mlx5/mlx5_ifc_macros.h b/include/linux/mlx5/mlx5_ifc_macros.h
index d357acfd351de2..be963b9ad5b295 100644
--- a/include/linux/mlx5/mlx5_ifc_macros.h
+++ b/include/linux/mlx5/mlx5_ifc_macros.h
@@ -85,6 +85,13 @@ __mlx5_mask(typ, fld))
__MLX5_SET64(typ, p, fld[idx], v); \
} while (0)

+#define MLX5_ARRAY_GET64(typ, p, fld, idx) \
+ ({ \
+ BUILD_BUG_ON(__mlx5_bit_sz(typ, fld) % 64); \
+ be64_to_cpu( \
+ *((__be64 *)(p) + __mlx5_64_off(typ, fld) + (idx))); \
+ })
+
#define MLX5_GET64(typ, p, fld) be64_to_cpu(*((__be64 *)(p) + __mlx5_64_off(typ, fld)))

#define MLX5_GET64_PR(typ, p, fld) ({ \
@@ -130,4 +137,49 @@ __mlx5_mask16(typ, fld))
tmp; \
})

+/*
+ * Use READ_ONCE/WRITE_ONCE for a single field that hardware may read/write
+ * unpredictably, mostly owner bits. All other bits in the DW must be stable.
+ * Usually a dma_wmb() will be required before a write and a dma_rmb() after a
+ * read.
+ */
+#define MLX5_GET_ONCE(typ, p, fld) \
+ ((be32_to_cpu(READ_ONCE(*((__be32 *)(p) + __mlx5_dw_off(typ, fld)))) >> \
+ __mlx5_dw_bit_off(typ, fld)) & \
+ __mlx5_mask(typ, fld))
+
+#define MLX5_SET_ONCE(typ, p, fld, v) \
+ do { \
+ u32 _v = v; \
+ __be32 *_dw = (__be32 *)(p) + __mlx5_dw_off(typ, fld); \
+ BUILD_BUG_ON(__mlx5_st_sz_bits(typ) % 32); \
+ WRITE_ONCE(*_dw, \
+ cpu_to_be32((be32_to_cpu(READ_ONCE(*_dw)) & \
+ (~__mlx5_dw_mask(typ, fld))) | \
+ (((_v) & __mlx5_mask(typ, fld)) \
+ << __mlx5_dw_bit_off(typ, fld)))); \
+ } while (0)
+
+/* Access MMIO registers, usually the init segment, using IFC structs. */
+#define MLX5_GET_MMIO(typ, p, fld) \
+ ((ioread32be(((__be32 __iomem *)(p) + __mlx5_dw_off(typ, fld))) >> \
+ __mlx5_dw_bit_off(typ, fld)) & \
+ __mlx5_mask(typ, fld))
+
+/* The set is not relaxed so there is an integrated dma_wmb(). */
+#define MLX5_SET_MMIO(typ, p, fld, v) \
+ do { \
+ u32 _v = v; \
+ void __iomem *_dw = \
+ ((__be32 __iomem *)(p) + __mlx5_dw_off(typ, fld)); \
+ if (__mlx5_bit_sz(typ, fld) == 32) \
+ iowrite32be(_v, _dw); \
+ else \
+ iowrite32be((ioread32be(_dw) & \
+ (~__mlx5_dw_mask(typ, fld))) | \
+ ((_v & __mlx5_mask(typ, fld)) \
+ << __mlx5_dw_bit_off(typ, fld)), \
+ _dw); \
+ } while (0)
+
#endif /* MLX5_IFC_MACROS_H */
--
2.43.0