linux-kernel - RE: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT

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Message-ID: <BN9PR11MB5276D8406BF08B853329288C8CB4A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Mon, 20 Nov 2023 08:09:35 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
CC:     "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Duan, Zhenzhong" <zhenzhong.duan@...el.com>,
        "joao.m.martins@...cle.com" <joao.m.martins@...cle.com>,
        "Zeng, Xin" <xin.zeng@...el.com>,
        "Zhao, Yan Y" <yan.y.zhao@...el.com>
Subject: RE: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE

> From: Liu, Yi L <yi.l.liu@...el.com>
> Sent: Friday, November 17, 2023 9:07 PM
> +
> +	hwpt = iommufd_hw_pagetable_get_nested(ucmd, cmd->hwpt_id);
> +	if (IS_ERR(hwpt))
> +		return PTR_ERR(hwpt);
> +
> +	rc = hwpt->domain->ops->cache_invalidate_user(hwpt->domain,
> &data_array,
> +						      &cmd-
> >out_driver_error_code);
> +	cmd->req_num = data_array.entry_num;
> +	if (iommufd_ucmd_respond(ucmd, sizeof(*cmd)))
> +		return -EFAULT;
> +	iommufd_put_object(&hwpt->obj);

the object is not put when ucmd response fails. It can be put right
after calling @cache_invalidate_user()

> @@ -309,6 +309,7 @@ union ucmd_buffer {
>  	struct iommu_hwpt_alloc hwpt;
>  	struct iommu_hwpt_get_dirty_bitmap get_dirty_bitmap;
>  	struct iommu_hwpt_set_dirty_tracking set_dirty_tracking;
> +	struct iommu_hwpt_invalidate cache;

In alphabetic order this should be put before "hwpt_set_dirty"

>  	struct iommu_ioas_alloc alloc;
>  	struct iommu_ioas_allow_iovas allow_iovas;
>  	struct iommu_ioas_copy ioas_copy;
> @@ -348,6 +349,8 @@ static const struct iommufd_ioctl_op
> iommufd_ioctl_ops[] = {
>  		 struct iommu_hwpt_get_dirty_bitmap, data),
>  	IOCTL_OP(IOMMU_HWPT_SET_DIRTY_TRACKING,
> iommufd_hwpt_set_dirty_tracking,
>  		 struct iommu_hwpt_set_dirty_tracking, __reserved),
> +	IOCTL_OP(IOMMU_HWPT_INVALIDATE, iommufd_hwpt_invalidate,
> +		 struct iommu_hwpt_invalidate, out_driver_error_code),

ditto

> +/**
> + * struct iommu_hwpt_invalidate - ioctl(IOMMU_HWPT_INVALIDATE)
> + * @size: sizeof(struct iommu_hwpt_invalidate)
> + * @hwpt_id: HWPT ID of a nested HWPT for cache invalidation

remove the first 'HWPT'

> + * @reqs_uptr: User pointer to an array having @req_num of cache
> invalidation
> + *             requests. The request entries in the array are of fixed width
> + *             @req_len, and contain a user data structure for invalidation
> + *             request specific to the given hardware page table.
> + * @req_type: One of enum iommu_hwpt_data_type, defining the data
> type of all
> + *            the entries in the invalidation request array. It should suit
> + *            with the data_type passed per the allocation of the hwpt pointed
> + *            by @hwpt_id.

"It should match the data_type given to the specified hwpt"

> + * @req_len: Length (in bytes) of a request entry in the request array
> + * @req_num: Input the number of cache invalidation requests in the array.
> + *           Output the number of requests successfully handled by kernel.
> + * @out_driver_error_code: Report a driver speicifc error code upon failure.
> + *                         It's optional, driver has a choice to fill it or
> + *                         not.

Being optional how does the user tell whether the code is filled or not?

> + *
> + * Invalidate the iommu cache for user-managed page table. Modifications
> on a
> + * user-managed page table should be followed by this operation to sync
> cache.
> + * Each ioctl can support one or more cache invalidation requests in the
> array
> + * that has a total size of @req_len * @req_num.
> + */
> +struct iommu_hwpt_invalidate {
> +	__u32 size;
> +	__u32 hwpt_id;
> +	__aligned_u64 reqs_uptr;
> +	__u32 req_type;
> +	__u32 req_len;
> +	__u32 req_num;
> +	__u32 out_driver_error_code;
> +};

Probably 'data_uptr', 'data_type', "entry_len' and 'entry_num" read slightly
better.