Re: [PATCH v5 2/9] iommu/arm-smmu-v3: Replace s1_cfg with cdtab_cfg
From: Will Deacon <will@kernel.org>
Date: 2023-08-09 16:23:03
Also in:
linux-iommu, lkml
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:quoted
On Wed, Aug 09, 2023 at 10:59:33AM -0300, Jason Gunthorpe wrote:quoted
On Wed, Aug 09, 2023 at 02:49:41PM +0100, Will Deacon wrote:quoted
quoted
@@ -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 :/quoted
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.quoted
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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel