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Date:   Tue, 6 Dec 2022 15:00:02 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Christoph Hellwig <hch@lst.de>, Lei Rao <lei.rao@intel.com>,
        kbusch@kernel.org, axboe@fb.com, kch@nvidia.com, sagi@grimberg.me,
        alex.williamson@redhat.com, cohuck@redhat.com, yishaih@nvidia.com,
        shameerali.kolothum.thodi@huawei.com, kevin.tian@intel.com,
        mjrosato@linux.ibm.com, linux-kernel@vger.kernel.org,
        linux-nvme@lists.infradead.org, kvm@vger.kernel.org,
        eddie.dong@intel.com, yadong.li@intel.com, yi.l.liu@intel.com,
        Konrad.wilk@oracle.com, stephen@eideticom.com, hang.yuan@intel.com
Subject: Re: [RFC PATCH 5/5] nvme-vfio: Add a document for the NVMe device
Message-ID: <20221206140002.GB27689@lst.de>
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On Tue, Dec 06, 2022 at 09:52:54AM -0400, Jason Gunthorpe wrote:
> On Tue, Dec 06, 2022 at 02:09:01PM +0100, Christoph Hellwig wrote:
> > On Tue, Dec 06, 2022 at 09:05:05AM -0400, Jason Gunthorpe wrote:
> > > In this case Intel has a real PCI SRIOV VF to expose to the guest,
> > > with a full VF RID.
> > 
> > RID?
> 
> "Requester ID" - PCI SIG term that in Linux basically means you get to
> assign an iommu_domain to the vfio device.

Yeah I now the Requester ID, I've just never seen that shortcut for it.

> >From what I understood this series basically allows two Intel devices
> to pass a big opaque blob of data. Intel didn't document what is in
> that blob, so I assume it captures everything you mention above.

Which would be just as bad, because it then changes the IDs under
the live OS on a restore.  This is not something that can be done
behind the back of the hypervisors / control plane OS.