[BUG] vmlinux.o: warning: objtool: iommu_dma_sw_msi() falls through to next function alloc_io_pgtable_ops()

[Paul E. McKenney]

Hello!

Building next-20250326 using clang version 19.1.7 (CentOS 19.1.7-1.el9)
gets me the following warning:

vmlinux.o: warning: objtool: iommu_dma_sw_msi() falls through to next function alloc_io_pgtable_ops()

This surprised me for a couple of reasons.  First, from what I
can see, iommu_dma_sw_msi() does not fall through.  Second, it
is in drivers/iommu/dma-iommu.c while alloc_io_pgtable_ops() is in
drivers/iommu/io-pgtable.c, though maybe the compiler and/or linker saw
fit to rearrange these functions' object code.

Please let me know of any debug patches or fixes that I could apply,
or any additional information that you might need.

						Thanx, Paul

Note to self: Run 2025.03.26-14.37.10-remote on first test system.  ;-)

------------------------------------------------------------------------

int iommu_dma_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
		     phys_addr_t msi_addr)
{
	struct device *dev = msi_desc_to_dev(desc);
	const struct iommu_dma_msi_page *msi_page;

	if (!has_msi_cookie(domain)) {
		msi_desc_set_iommu_msi_iova(desc, 0, 0);
		return 0;
	}

	iommu_group_mutex_assert(dev);
	msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);
	if (!msi_page)
		return -ENOMEM;

	msi_desc_set_iommu_msi_iova(desc, msi_page->iova,
				    ilog2(cookie_msi_granule(domain)));
	return 0;
}