Re: [RFC] Legacy Virtio Driver with Device Has Limited Memory Access

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2024年6月18日(火) 19:33 Michael S. Tsirkin <mst@xxxxxxxxxx>:
>
> On Tue, Jun 18, 2024 at 07:15:47PM +0900, Shunsuke Mie wrote:
> > Thank you for your response.
> >
> > 2024年6月18日(火) 18:47 Michael S. Tsirkin <mst@xxxxxxxxxx>:
> > >
> > > On Tue, Jun 18, 2024 at 08:41:09AM +0900, Shunsuke Mie wrote:
> > > > Let's clarify the situation.
> > > >
> > > > The Virtio device and driver are not working properly due to a
> > > > combination of the following reasons:
> > > >
> > > > 1. Regarding VIRTIO_F_ACCESS_PLATFORM:
> > > > - The modern spec includes VIRTIO_F_ACCESS_PLATFORM, which allows
> > > > Physical DMAC to be used.
> > > > - This feature is not available in the legacy spec.
> > >
> > > ... because legacy drivers don't set it
> > >
> > > > 2. Regarding Virtio PCIe Capability:
> > > > - The modern spec requires Virtio PCIe Capability.
> > >
> > > It's a PCI capability actually. People have been asking
> > > about option to make it a pcie extended capability,
> > > but no one did the spec, qemu and driver work, yet.
> > >
> > > > - In some environments, Virtio PCIe Capability cannot be provided.
> > >
> > > why not?
> > PCIe Endpoint Controller chips are available from several vendors and allow
> > software to describe the behavior of PCIe Endpoint functions. However, they
> > offer only limited functionality. Specifically, while PCIe bus communication is
> > programmable, PCIe Capabilities are fixed and cannot be made to show as
> > virtio's.
>
> Okay. So where could these structures live, if not in pci config?
What does "these structures" refer to? PCIe Capabilities? virtio configs?
> --
> MST
>





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