Re: [PATCH rdma-next v3 01/10] RDMA/mana_ib: Allocate and map fast-registration MRs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] rdma: brittle ALIGN() macro usage with struct size
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commit 5c377dbd75ff20b57d34b69b57ca784c487e1850
Author: Konstantin Taranov <kotaranov@microsoft.com>

RDMA/mana_ib: Allocate and map fast-registration MRs

Implement alloc_mr and map_mr_sg for memory-registration MRs.

> diff --git a/drivers/infiniband/hw/mana/mana_ib.h b/drivers/infiniband/hw/mana/mana_ib.h
> index 9173ca64d2e1e..3098ad2c6a05c 100644
> --- a/drivers/infiniband/hw/mana/mana_ib.h
> +++ b/drivers/infiniband/hw/mana/mana_ib.h
[ ... ]
> +struct mana_fmr_mst_entry {
> +	u32 reserved1;
> +	u32 reserved2		: 8;
> +	u32 page_size		: 5;
> +	u32 reserved3		: 3;
> +	u32 access_right	: 8;
> +	u32 addr_type		: 2;
> +	u32 reserved4		: 6;
> +	u32 reserved5[2];
> +	u64 start_va;
> +	u64 length;
> +	u32 reserved6[8];
> +}; /* HW DATA */
> +
> +static inline u32 mana_ib_fmr_header_offset(u32 num_ptes)
> +{
> +	/* the header is located after the PTEs and aligned to mst entry */
> +	return ALIGN(sizeof(u64) * num_ptes, sizeof(struct mana_fmr_mst_entry));
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[Severity: Low]
Is it safe to use ALIGN() with a structure size in mana_ib_fmr_header_offset?

The ALIGN(x, a) macro strictly requires the alignment argument 'a' to be a
power of two in order to perform its bitwise masking logic correctly.

While sizeof(struct mana_fmr_mst_entry) currently evaluates to exactly 64 bytes
and works properly, using a structure's total size for alignment bounds is
brittle. If a developer later modifies the hardware structure in a way that its
size is no longer a power of two, the ALIGN() macro will compile without error
but produce silently corrupted mathematical results at runtime.

Could a constant macro defining the expected power-of-two alignment boundary be
used here instead?

> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20261007153330.2979799-1-kotaranov@linux.microsoft.com?part=1