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From:   Jason Wang <jasowang@redhat.com>
Date:   Mon, 20 Feb 2023 10:36:27 +0800
Message-ID: <CACGkMEuDG1NUs0=ry1=Mphfd+TrqAvVS0yeu9hcni2VrPkB8tQ@mail.gmail.com>
Subject: Re: [PATCH v2] vhost/vdpa: Add MSI translation tables to iommu for
 software-managed MSI
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Jason Gunthorpe <jgg@nvidia.com>,
        Nanyong Sun <sunnanyong@huawei.com>, joro@8bytes.org,
        will@kernel.org, robin.murphy@arm.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
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On Fri, Feb 17, 2023 at 6:11 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Feb 17, 2023 at 01:35:59PM +0800, Jason Wang wrote:
> > 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.
>
> Hmm do we? this looks like it's enabling new platforms is not a bugfix...

I think we haven't limited vDPA to any specific arch in the past?

Thanks

>
> > >
> > > 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
> > >
>