Re: [PATCH 7/9] iommupt/x86: Support SW bits and permit PT_FEAT_DMA_INCOHERENT

[Baolu Lu <baolu.lu@linux.intel.com>]

On 7/17/25 03:57, Jason Gunthorpe wrote:
> VT-D requires PT_FEAT_DMA_INCOHERENT for the x86 page table as well,
> implement the required SW bits and enable the feature.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>   drivers/iommu/generic_pt/fmt/iommu_x86_64.c |  2 +-
>   drivers/iommu/generic_pt/fmt/x86_64.h       | 27 +++++++++++++++++++++
>   2 files changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/generic_pt/fmt/iommu_x86_64.c b/drivers/iommu/generic_pt/fmt/iommu_x86_64.c
> index 5c5960d871a32f..5472660c2d7156 100644
> --- a/drivers/iommu/generic_pt/fmt/iommu_x86_64.c
> +++ b/drivers/iommu/generic_pt/fmt/iommu_x86_64.c
> @@ -6,6 +6,6 @@
>   #define PT_SUPPORTED_FEATURES                                  \
>   	(BIT(PT_FEAT_SIGN_EXTEND) | BIT(PT_FEAT_FLUSH_RANGE) | \
>   	 BIT(PT_FEAT_FLUSH_RANGE_NO_GAPS) |                    \
> -	 BIT(PT_FEAT_X86_64_AMD_ENCRYPT_TABLES))
> +	 BIT(PT_FEAT_X86_64_AMD_ENCRYPT_TABLES) | BIT(PT_FEAT_DMA_INCOHERENT))
>   
>   #include "iommu_template.h"
> diff --git a/drivers/iommu/generic_pt/fmt/x86_64.h b/drivers/iommu/generic_pt/fmt/x86_64.h
> index 60f8bd6b164b54..1b691f7cbf82d8 100644
> --- a/drivers/iommu/generic_pt/fmt/x86_64.h
> +++ b/drivers/iommu/generic_pt/fmt/x86_64.h
> @@ -160,6 +160,33 @@ static inline void x86_64_pt_attr_from_entry(const struct pt_state *pts,
>   }
>   #define pt_attr_from_entry x86_64_pt_attr_from_entry
>   
> +static inline unsigned int x86_64_pt_max_sw_bit(struct pt_common *common)
> +{
> +	return 12;
> +}
> +#define pt_max_sw_bit x86_64_pt_max_sw_bit
> +
> +static inline u64 x86_64_pt_sw_bit(unsigned int bitnr)
> +{
> +	/* Bits marked Ignored/AVL in the specification */
> +	switch (bitnr) {
> +	case 0:
> +		return BIT(9);
> +	case 1:
> +		return BIT(11);
> +	case 2 ... 12:
> +		return BIT_ULL((bitnr - 2) + 52);

Just out of curiosity, why bit 63 can't be used as the sw bit?

> +	/* Remaing bits 9-8,6,4,3  are only available in some entries */
> +	default:
> +		if (__builtin_constant_p(bitnr))
> +			BUILD_BUG();
> +		else
> +			PT_WARN_ON(true);
> +		return 0;
> +	}
> +}
> +#define pt_sw_bit x86_64_pt_sw_bit
> +
>   /* --- iommu */
>   #include <linux/generic_pt/iommu.h>
>   #include <linux/iommu.h>

Looks good to me.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Thanks,
baolu