linux-kernel - Re: [PATCH v5 07/11] iommufd: Add data structure for Intel VT-d stage-1 cache invalidation

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Message-ID: <e493c62d-8f10-17c8-f660-dbae19c481a4@linux.intel.com>
Date:   Thu, 21 Sep 2023 21:33:38 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Yi Liu <yi.l.liu@...el.com>, joro@...tes.org,
        alex.williamson@...hat.com, jgg@...dia.com, kevin.tian@...el.com,
        robin.murphy@....com
Cc:     baolu.lu@...ux.intel.com, cohuck@...hat.com, eric.auger@...hat.com,
        nicolinc@...dia.com, kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.y.sun@...ux.intel.com,
        peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        zhenzhong.duan@...el.com, joao.m.martins@...cle.com
Subject: Re: [PATCH v5 07/11] iommufd: Add data structure for Intel VT-d
 stage-1 cache invalidation

On 2023/9/21 15:54, Yi Liu wrote:
> This adds the data structure for flushing iotlb for the nested domain
> allocated with IOMMU_HWPT_TYPE_VTD_S1 type.
> 
> This only supports invalidating IOTLB, but no for device-TLB as device-TLB
> invalidation will be covered automatically in the IOTLB invalidation if the
> underlying IOMMU driver has enabled ATS for the affected device.
> 
> Signed-off-by: Yi Liu <yi.l.liu@...el.com>
> ---
>   include/uapi/linux/iommufd.h | 34 ++++++++++++++++++++++++++++++++++
>   1 file changed, 34 insertions(+)
> 
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 18a502e206c3..3050efbceb57 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -510,6 +510,40 @@ struct iommu_hw_info {
>   };
>   #define IOMMU_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_GET_HW_INFO)
>   
> +/**
> + * enum iommu_hwpt_vtd_s1_invalidate_flags - Flags for Intel VT-d
> + *                                           stage-1 cache invalidation
> + * @IOMMU_VTD_QI_FLAGS_LEAF: The LEAF flag indicates whether only the
> + *                           leaf PTE caching needs to be invalidated
> + *                           and other paging structure caches can be
> + *                           preserved.
> + */
> +enum iommu_hwpt_vtd_s1_invalidate_flags {
> +	IOMMU_VTD_QI_FLAGS_LEAF = 1 << 0,
> +};
> +
> +/**
> + * struct iommu_hwpt_vtd_s1_invalidate - Intel VT-d cache invalidation
> + *                                       (IOMMU_HWPT_TYPE_VTD_S1)
> + * @addr: The start address of the addresses to be invalidated.

Is there an alignment requirement for @addr? If so, is 4K alignment
sufficient? Perhaps we need to document it here so that user space can
calculate the @addr correctly.

> + * @npages: Number of contiguous 4K pages to be invalidated.
> + * @flags: Combination of enum iommu_hwpt_vtd_s1_invalidate_flags
> + * @__reserved: Must be 0
> + *
> + * The Intel VT-d specific invalidation data for user-managed stage-1 cache
> + * invalidation under nested translation. Userspace uses this structure to
> + * tell host about the impacted caches after modifying the stage-1 page table.
> + *
> + * Invalidating all the caches related to the page table by setting @addr
> + * to be 0 and @npages to be __aligned_u64(-1).
> + */
> +struct iommu_hwpt_vtd_s1_invalidate {
> +	__aligned_u64 addr;
> +	__aligned_u64 npages;
> +	__u32 flags;
> +	__u32 __reserved;
> +};
> +
>   /**
>    * struct iommu_hwpt_invalidate - ioctl(IOMMU_HWPT_INVALIDATE)
>    * @size: sizeof(struct iommu_hwpt_invalidate)

Best regards,
baolu