Date:   Fri, 17 Feb 2023 05:11:38 -0500
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Jason Wang <jasowang@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
Subject: Re: [PATCH v2] vhost/vdpa: Add MSI translation tables to iommu for
 software-managed MSI
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References: <20230207120843.1580403-1-sunnanyong@huawei.com>
 <Y+7G+tiBCjKYnxcZ@nvidia.com>
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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...

> >
> > 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
> >