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

Keqian Zhu
2021-03-02T15:57:27Z

Hi Robin,

I am going to send v2 at next week, to addresses these issues reported by you. Many thanks!
And do you have any further comments on patch #4 #5 and #6?

Thanks,
Keqian

On 2021/2/5 3:50, Robin Murphy wrote:
> 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;
>>
> .
>