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From:   Michael Shavit <mshavit@google.com>
Date:   Fri, 11 Aug 2023 01:15:14 +0800
Message-ID: <CAKHBV254QmO3iXyEL6w0PqvVofm_UCDd13LKmpbhU-cEORB5ww@mail.gmail.com>
Subject: Re: [PATCH v5 2/9] iommu/arm-smmu-v3: Replace s1_cfg with cdtab_cfg
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Will Deacon <will@kernel.org>, iommu@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        robin.murphy@arm.com, nicolinc@nvidia.com, jean-philippe@linaro.org
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> > > What dead code? Is the deal here that we keep the field, but still
> > > infer the value to write from (cd_table->l1_desc == null) in
> > > arm_smmu_write_strtab_ent??
> >
> > Keep the field and write it directly when populating the ste (i.e. don't
> > infer anything), but the field moves into 'struct arm_smmu_ctx_desc_cfg'.
>
> Yes - the 'dead code' is that we introduce storage for a field that is
> always a known constant (STRTAB_STE_0_S1FMT_64K_L2).

I'm not sure we're on the same page here. s1fmt could contain either
`STRTAB_STE_0_S1FMT_64K_L2` or `STRTAB_STE_0_S1FMT_LINEAR`, and this
value will be directly copied in arm_smmu_write_strtab_ent.