Messages in this thread | | | Date | Wed, 9 Aug 2023 17:22:54 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v5 2/9] iommu/arm-smmu-v3: Replace s1_cfg with cdtab_cfg |
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On Wed, Aug 09, 2023 at 12:08:02PM -0300, Jason Gunthorpe wrote: > On Wed, Aug 09, 2023 at 03:55:43PM +0100, Will Deacon wrote: > > On Wed, Aug 09, 2023 at 10:59:33AM -0300, Jason Gunthorpe wrote: > > > On Wed, Aug 09, 2023 at 02:49:41PM +0100, Will Deacon wrote: > > > > > > > > @@ -1360,10 +1357,14 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid, > > > > > !master->stall_enabled) > > > > > dst[1] |= cpu_to_le64(STRTAB_STE_1_S1STALLD); > > > > > > > > > > - val |= (s1_cfg->cdcfg.cdtab_dma & STRTAB_STE_0_S1CTXPTR_MASK) | > > > > > - FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_S1_TRANS) | > > > > > - FIELD_PREP(STRTAB_STE_0_S1CDMAX, s1_cfg->s1cdmax) | > > > > > - FIELD_PREP(STRTAB_STE_0_S1FMT, s1_cfg->s1fmt); > > > > > + val |= (cd_table->cdtab_dma & STRTAB_STE_0_S1CTXPTR_MASK) | > > > > > + FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_S1_TRANS) | > > > > > + FIELD_PREP(STRTAB_STE_0_S1CDMAX, > > > > > + cd_table->max_cds_bits) | > > > > > + FIELD_PREP(STRTAB_STE_0_S1FMT, > > > > > + cd_table->l1_desc ? > > > > > + STRTAB_STE_0_S1FMT_64K_L2 : > > > > > + STRTAB_STE_0_S1FMT_LINEAR); > > > > > > > > magically know that we're using 64k tables. > > > > > > > > Why is this an improvement to the driver? > > > > > > Put the above in a function > > > > > > arm_smmu_get_cd_ste(struct arm_smmu_ctx_desc_cfg *cdtab, void *ste) > > > > > > And it makes more sense. > > > > Sorry, but I'm not seeing it :/ > > > > > We don't need the driver to precompute the "s1_cfg" parameters and > > > store them in a redundant struct along side the ctx_desc_cfg when we > > > can compute those same values on the fly with no cost. > > > > But the computation isn't happening -- the STRTAB_STE_0_S1FMT_64K_L2 > > constant is hardcoded here. > > So it would be hard coded in arm_smmu_get_cd_ste() because that > reflects the current state of CD table code. > > > If we want to use 4k leaf tables in some cases, how would you add > > that? Such a change shouldn't need the low-level strtab creation > > code to change. > > You would modify arm_smmu_ctx_desc_cfg to teach it about the different > format. It would gain some (enum?) member that specifies the CD table > layout and geometry. arm_smmu_get_cd_ste() will interpret that member > and generate the correct STE for the specifc cd table.
Sounds a lot like the existing s1fmt field. Can we keep it?
Will
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