Re: [PATCH v7 14/24] iommu/arm-smmu-v3: Add SVA feature checking

Will Deacon
2020-05-21T14:17:22Z

On Tue, May 19, 2020 at 07:54:52PM +0200, Jean-Philippe Brucker wrote:
> Aggregate all sanity-checks for sharing CPU page tables with the SMMU
> under a single ARM_SMMU_FEAT_SVA bit. For PCIe SVA, users also need to
> check FEAT_ATS and FEAT_PRI. For platform SVA, they will most likely have
> to check FEAT_STALLS.
>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> drivers/iommu/arm-smmu-v3.c | 72 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 72 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 9332253e3608..a9f6f1d7014e 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -660,6 +660,7 @@ struct arm_smmu_device {
> #define ARM_SMMU_FEAT_RANGE_INV (1 << 15)
> #define ARM_SMMU_FEAT_E2H (1 << 16)
> #define ARM_SMMU_FEAT_BTM (1 << 17)
> +#define ARM_SMMU_FEAT_SVA (1 << 18)
> u32 features;
>
> #define ARM_SMMU_OPT_SKIP_PREFETCH (1 << 0)
> @@ -3935,6 +3936,74 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
> return 0;
> }
>
> +static bool arm_smmu_supports_sva(struct arm_smmu_device *smmu)
> +{
> + unsigned long reg, fld;
> + unsigned long oas;
> + unsigned long asid_bits;
> +
> + u32 feat_mask = ARM_SMMU_FEAT_BTM | ARM_SMMU_FEAT_COHERENCY;

Aha -- here's the coherency check I missed!

> +
> + if ((smmu->features & feat_mask) != feat_mask)
> + return false;
> +
> + if (!(smmu->pgsize_bitmap & PAGE_SIZE))
> + return false;
> +
> + /*
> + * Get the smallest PA size of all CPUs (sanitized by cpufeature). We're
> + * not even pretending to support AArch32 here.
> + */
> + reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
> + fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR0_PARANGE_SHIFT);
> + switch (fld) {
> + case 0x0:
> + oas = 32;
> + break;
> + case 0x1:
> + oas = 36;
> + break;
> + case 0x2:
> + oas = 40;
> + break;
> + case 0x3:
> + oas = 42;
> + break;
> + case 0x4:
> + oas = 44;
> + break;
> + case 0x5:
> + oas = 48;
> + break;
> + case 0x6:

We can use ID_AA64MMFR0_PARANGE_xx constants instead of the hardcoded hex
numbers here.

With that:

Acked-by: Will Deacon <will@kernel.org>

Will