Re: [PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation for AmpereOne
From: James Morse
Date: Wed Oct 02 2024 - 12:58:25 EST
Hello!
On 01/10/2024 19:03, Yang Shi wrote:
> The commit ce410410f1a7 ("iommu/arm-smmu-v3: Add arm_smmu_strtab_l1/2_idx()")
> calculated the last index of L1 stream table by 1 << smmu->sid_bits. 1
> is 32 bit value.
> However AmpereOne has 32-bit stream id size. This resulted in
> ouf-of-bound shift. The disassembly of shift is:
>
> ldr w2, [x19, 828] //, smmu_7(D)->sid_bits
> mov w20, 1
> lsl w20, w20, w2
>
> According to ARM spec, if the registers are 32 bit, the instruction actually
> does:
> dest = src << (shift % 32)
>
> So it actually shifted by zero bit.
>
> This caused v6.12-rc1 failed to boot on AmpereOne
Same here - one of arm's reference designs prints 1 giga-tonne of:
| arm-smmu-v3 arm-smmu-v3.5.auto: event 0x02 received:
| arm-smmu-v3 arm-smmu-v3.5.auto: 0x0000c90000000002
| arm-smmu-v3 arm-smmu-v3.5.auto: 0x0000000000000000
| arm-smmu-v3 arm-smmu-v3.5.auto: 0x0000000000000000
| arm-smmu-v3 arm-smmu-v3.5.auto: 0x0000000000000000
during boot - then fails to find the nvme.
Bisect points to ce410410f1a7, and the below diff fixes it.
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 737c5b882355..01a2faee04bc 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -3625,7 +3625,7 @@ static int arm_smmu_init_strtab_2lvl(struct arm_smmu_device *smmu)
> u32 l1size;
> struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
> unsigned int last_sid_idx =
> - arm_smmu_strtab_l1_idx((1 << smmu->sid_bits) - 1);
> + arm_smmu_strtab_l1_idx((1UL << smmu->sid_bits) - 1);
>
> /* Calculate the L1 size, capped to the SIDSIZE. */
> cfg->l2.num_l1_ents = min(last_sid_idx + 1, STRTAB_MAX_L1_ENTRIES);
Tested-by: James Morse <james.morse@xxxxxxx>
Thanks,
James