Re: [PATCH 2/2][RFC] KVM: Emulate MSI-X table and PBA in kernel

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jan 02, 2011 at 03:34:21PM +0200, Avi Kivity wrote:
> On 01/02/2011 01:51 PM, Michael S. Tsirkin wrote:
> >>  >
> >>  >I don't see how userspace can send interrupts with this
> >>  >interface unfortunately. We also need irqfd support ...
> >>
> >>  Sure we'll need additions to that interface.
> >
> >What I suggested is
> >1. an ioctl to map phy address + size to table id
> >2. a new gsi type with a table id + entry number.
> >
> >If we have that, assigned devices, virtio and vhost-net can work
> >mostly as is, with just the mask bits accelerated.
> >
> 
> Ok.  Please adopt this patch and send a series that does this.  I'd
> like to see the whole thing working.
> 
> >>  What about vhost-net and vfio?  I thought that they could emulate
> >>  the mask bits:
> >>
> >>  - KVM_MMIOFD(vmfd, mmio_range, fd1, fd2) associates an mmio range with an fd
> >>  - writel(mmio_range) or readl(mmio_range) from the guest causes a
> >>  command to be written to fd1
> >>  - for readl(), read from fd2 to see the result (works nicely for
> >>  "pci read flushes posted writes")
> >>
> >>  this allows interesting stuff to be implemented in separate
> >>  processes, threads, or kernel modules.
> >
> >This could work. Some thought needs to be given to how we make sure that
> >an appropriate type of file is passed in. Maybe using a netlink
> >based connector for this a good idea?
> 
> Why do we care what type of file is passed?  We just write there,
> and whatever is on the other side needs to handle it.
> 
> >OTOH if we have MSIX mask bit emulation in kvm anyway, using it makes
> >sense ...
> 
> Yeah, except I'm not sure how the current proposal can interface
> with vfio.

Me too.

>  So we'll have two interfaces, until we vfio takes over
> completely.
> -- 
> error compiling committee.c: too many arguments to function