linux-kernel - Re: [PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation for AmpereOne

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Message-ID: <20241001191800.GA1369530@ziepe.ca>
Date: Tue, 1 Oct 2024 16:18:00 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Yang Shi <yang@...amperecomputing.com>
Cc: Nicolin Chen <nicolinc@...dia.com>, will@...nel.org,
	robin.murphy@....com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation
 for AmpereOne

On Tue, Oct 01, 2024 at 12:09:03PM -0700, Yang Shi wrote:
> > Also, there are other places doing "1 << smmu->sid_bits", e.g.
> > arm_smmu_init_strtab_linear().
> 
> The disassembly shows it uses "sbfiz x21, x20, 6, 32" instead of lsl. 1UL
> should be used if we want to take extra caution and don't prefer rely on
> compiler.

Still, we should be fixing them all if sid_bits == 32, all those
shifts should be throwing a UBSAN error. It would be crazy to have a
32 bit linear table but I guess it is allowed?

Jason