Re: [PATCH 5/5] vfio-pci: Allow to mmap MSI-X table if interrupt remapping is supported

[Yongji Xie]

On 2016/5/3 13:34, Tian, Kevin wrote:

> > From: Yongji Xie
> > Sent: Wednesday, April 27, 2016 8:43 PM
> >
> > This patch enables mmapping MSI-X tables if hardware supports
> > interrupt remapping which can ensure that a given pci device
> > can only shoot the MSIs assigned for it.
> >
> > With MSI-X table mmapped, we also need to expose the
> > read/write interface which will be used to access MSI-X table.
> >
> > Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> A curious question here. Does "allow to mmap MSI-X" essentially
> mean that KVM guest can directly read/write physical MSI-X
> structure then?
>
> Thanks
> Kevin

Here we just allow to mmap MSI-X table in kernel. It doesn't
mean all KVM guest can directly read/write physical MSI-X
structure. This should be decided by QEMU. For PPC64
platform, we would allow to passthrough the MSI-X table
because we know guest kernel would not write physical
MSI-X structure when enabling MSI.

Thanks,
Yongji