Re: [RFC PATCH 01/11] iommu/arm-smmu-v3: Add feature detection for HTTU

Robin Murphy
2021-02-04T20:17:52Z

On 2021-01-28 15:17, Keqian Zhu wrote:
> From: jiangkunkun <jiangkunkun@huawei.com>
>
> The SMMU which supports HTTU (Hardware Translation Table Update) can
> update the access flag and the dirty state of TTD by hardware. It is
> essential to track dirty pages of DMA.
>
> This adds feature detection, none functional change.
>
> Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++++
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 8 ++++++++
> include/linux/io-pgtable.h | 1 +
> 3 files changed, 25 insertions(+)
>
> 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 8ca7415d785d..0f0fe71cc10d 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -1987,6 +1987,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
> .pgsize_bitmap = smmu->pgsize_bitmap,
> .ias = ias,
> .oas = oas,
> + .httu_hd = smmu->features & ARM_SMMU_FEAT_HTTU_HD,
> .coherent_walk = smmu->features & ARM_SMMU_FEAT_COHERENCY,
> .tlb = &arm_smmu_flush_ops,
> .iommu_dev = smmu->dev,
> @@ -3224,6 +3225,21 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
> if (reg & IDR0_HYP)
> smmu->features |= ARM_SMMU_FEAT_HYP;
>
> + switch (FIELD_GET(IDR0_HTTU, reg)) {

We need to accommodate the firmware override as well if we need this to
be meaningful. Jean-Philippe is already carrying a suitable patch in the
SVA stack[1].

> + case IDR0_HTTU_NONE:
> + break;
> + case IDR0_HTTU_HA:
> + smmu->features |= ARM_SMMU_FEAT_HTTU_HA;
> + break;
> + case IDR0_HTTU_HAD:
> + smmu->features |= ARM_SMMU_FEAT_HTTU_HA;
> + smmu->features |= ARM_SMMU_FEAT_HTTU_HD;
> + break;
> + default:
> + dev_err(smmu->dev, "unknown/unsupported HTTU!\n");
> + return -ENXIO;
> + }
> +
> /*
> * The coherency feature as set by FW is used in preference to the ID
> * register, but warn on mismatch.
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index 96c2e9565e00..e91bea44519e 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -33,6 +33,10 @@
> #define IDR0_ASID16 (1 << 12)
> #define IDR0_ATS (1 << 10)
> #define IDR0_HYP (1 << 9)
> +#define IDR0_HTTU GENMASK(7, 6)
> +#define IDR0_HTTU_NONE 0
> +#define IDR0_HTTU_HA 1
> +#define IDR0_HTTU_HAD 2
> #define IDR0_COHACC (1 << 4)
> #define IDR0_TTF GENMASK(3, 2)
> #define IDR0_TTF_AARCH64 2
> @@ -286,6 +290,8 @@
> #define CTXDESC_CD_0_TCR_TBI0 (1ULL << 38)
>
> #define CTXDESC_CD_0_AA64 (1UL << 41)
> +#define CTXDESC_CD_0_HD (1UL << 42)
> +#define CTXDESC_CD_0_HA (1UL << 43)
> #define CTXDESC_CD_0_S (1UL << 44)
> #define CTXDESC_CD_0_R (1UL << 45)
> #define CTXDESC_CD_0_A (1UL << 46)
> @@ -604,6 +610,8 @@ struct arm_smmu_device {
> #define ARM_SMMU_FEAT_RANGE_INV (1 << 15)
> #define ARM_SMMU_FEAT_BTM (1 << 16)
> #define ARM_SMMU_FEAT_SVA (1 << 17)
> +#define ARM_SMMU_FEAT_HTTU_HA (1 << 18)
> +#define ARM_SMMU_FEAT_HTTU_HD (1 << 19)
> u32 features;
>
> #define ARM_SMMU_OPT_SKIP_PREFETCH (1 << 0)
> diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> index ea727eb1a1a9..1a00ea8562c7 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -97,6 +97,7 @@ struct io_pgtable_cfg {
> unsigned long pgsize_bitmap;
> unsigned int ias;
> unsigned int oas;
> + bool httu_hd;

This is very specific to the AArch64 stage 1 format, not a generic
capability - I think it should be a quirk flag rather than a common field.

Robin.

[1]
https://jpbrucker.net/git/linux/commit/?h=sva/current&id=1ef7d512fb9082450dfe0d22ca4f7e35625a097b

> bool coherent_walk;
> const struct iommu_flush_ops *tlb;
> struct device *iommu_dev;
>