MIME-Version: 1.0
References: <20230207120843.1580403-1-sunnanyong@huawei.com> <Y+7G+tiBCjKYnxcZ@nvidia.com>
In-Reply-To: <Y+7G+tiBCjKYnxcZ@nvidia.com>
From:   Jason Wang <jasowang@redhat.com>
Date:   Fri, 17 Feb 2023 13:35:59 +0800
Message-ID: <CACGkMEtehykvqNUnfCi0VmHR1xpmhj4sSWdYW1-0oATY=0YhXw@mail.gmail.com>
Subject: Re: [PATCH v2] vhost/vdpa: Add MSI translation tables to iommu for
 software-managed MSI
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Nanyong Sun <sunnanyong@huawei.com>, joro@8bytes.org,
        will@kernel.org, robin.murphy@arm.com, mst@redhat.com,
        iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, wangrong68@huawei.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Feb 17, 2023 at 8:15 AM Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> On Tue, Feb 07, 2023 at 08:08:43PM +0800, Nanyong Sun wrote:
> > From: Rong Wang <wangrong68@huawei.com>
> >
> > Once enable iommu domain for one device, the MSI
> > translation tables have to be there for software-managed MSI.
> > Otherwise, platform with software-managed MSI without an
> > irq bypass function, can not get a correct memory write event
> > from pcie, will not get irqs.
> > The solution is to obtain the MSI phy base address from
> > iommu reserved region, and set it to iommu MSI cookie,
> > then translation tables will be created while request irq.
>
> Probably not what anyone wants to hear, but I would prefer we not add
> more uses of this stuff. It looks like we have to get rid of
> iommu_get_msi_cookie() :\
>
> I'd like it if vdpa could move to iommufd not keep copying stuff from
> it..

Yes, but we probably need a patch for -stable.

>
> Also the iommu_group_has_isolated_msi() check is missing on the vdpa
> path, and it is missing the iommu ownership mechanism.

Ok.

>
> Also which in-tree VDPA driver that uses the iommu runs on ARM? Please

ifcvf and vp_vpda are two drivers that use platform IOMMU.

Thanks

> don't propose core changes for unmerged drivers. :(
>
> Jason
>