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

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Date:   Thu, 7 Dec 2023 09:04:00 +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: Thursday, December 7, 2023 2:59 PM
> 
> On 2023/11/17 21:07, Yi Liu wrote:
> > @@ -613,4 +614,38 @@ struct iommu_hwpt_get_dirty_bitmap {
> >   #define IOMMU_HWPT_GET_DIRTY_BITMAP _IO(IOMMUFD_TYPE, \
> >
> 	IOMMUFD_CMD_HWPT_GET_DIRTY_BITMAP)
> >
> > +/**
> > + * 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
> > + * @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.
> 
> @Jason and Kevin,
> 
> Here a check with you two. I had a conversation with Nic on the definition
> of req_type here. It was added to support potential multiple kinds of cache
> invalidation data types for a invalidating cache for a single hwpt type[1].
> But we defined it as reusing the hwpt_data_type. In this way, it is not
> able to support the potential case in[1]. is it? Shall we define a separate
> enum for invalidation data types? And how can we let user know the
> available invalidation data types for a hwpt type? Any idea?
> 
> [1] https://lore.kernel.org/linux-
> iommu/20231018163720.GA3952@...dia.com/
> 

From that thread Jason mentioned to make the invalidation format
part of domain allocation. If that is the direction to go then there
won't be multiple invalidation formats per hwpt. The user should
create multiple hwpt's per invalidation format (though mixing
formats in one virtual platform is very unlikely)?