linux-kernel - Re: [PATCH] iommu: Convert unreachable() to BUG()

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Message-ID: <Z+VL4osULGr7tHwX@nvidia.com>
Date: Thu, 27 Mar 2025 10:00:18 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev, Peter Zijlstra <peterz@...radead.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	"Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH] iommu: Convert unreachable() to BUG()

On Wed, Mar 26, 2025 at 10:28:46PM -0700, Josh Poimboeuf wrote:
> Bare unreachable() should be avoided as it generates undefined behavior,
> e.g. falling through to the next function.  Use BUG() instead so the
> error is defined.
> 
> Fixes the following warnings:
> 
>   drivers/iommu/dma-iommu.o: warning: objtool: iommu_dma_sw_msi+0x92: can't find jump dest instruction at .text+0x54d5
>   vmlinux.o: warning: objtool: iommu_dma_get_msi_page() falls through to next function __iommu_dma_unmap()
> 
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Closes: https://lore.kernel.org/314f8809-cd59-479b-97d7-49356bf1c8d1@infradead.org
> Reported-by: Paul E. McKenney <paulmck@...nel.org>
> Closes: https://lore.kernel.org/5dd1f35e-8ece-43b7-ad6d-86d02d2718f6@paulmck-laptop
> Fixes: 6aa63a4ec947 ("iommu: Sort out domain user data")
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> ---
>  drivers/iommu/dma-iommu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

The offending patch is in the iommufd tree, so applied thanks for the
quick response

Jason