linux-kernel - Re: [PATCH v2] vhost/vdpa: Add MSI translation tables to iommu for software-managed MSI

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Message-ID: <b2c24e31-a708-8556-0029-93c0aa22a6ef@huawei.com>
Date:   Thu, 23 Mar 2023 20:15:44 +0800
From:   Nanyong Sun <sunnanyong@...wei.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, <joro@...tes.org>,
        <will@...nel.org>, <robin.murphy@....com>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>,
        <netdev@...r.kernel.org>, <wangrong68@...wei.com>,
        Cindy Lu <lulu@...hat.com>
Subject: Re: [PATCH v2] vhost/vdpa: Add MSI translation tables to iommu for
 software-managed MSI

On 2023/3/23 19:31, Jason Gunthorpe wrote:

> On Thu, Mar 23, 2023 at 05:22:36PM +0800, Nanyong Sun wrote:
>>> A patch to export that function is alread posted:
>>>
>>> https://lore.kernel.org/linux-iommu/BN9PR11MB52760E9705F2985EACCD5C4A8CBA9@BN9PR11MB5276.namprd11.prod.outlook.com/T/#u
>>>
>>> But I do not want VDPA to mis-use it unless it also implements all the
>>> ownership stuff properly.
>>>
>> I want to confirm if we need to introduce iommu group logic to vdpa, as "all
>> the ownership stuff" ?
> You have to call iommu_device_claim_dma_owner()
>
> But again, this is all pointless, iommufd takes are of all of this and
> VDPA should switch to it instead of more hacking.
>
> Jason
> .
Yeah,  thanks for your suggestion，but as Michael and Jason Wang said, 
before iommufd is ready, we may need to make vDPA work well on software 
managed MSI platforms.
To achieve that, basically we have two ways:

1. export iommu_get_resv_regions, and get regions device by device.
2. introduce iommu group, get regions by iommu_get_group_resv_regions, 
which already exported.