Re: [Xen-devel] Xen 4.2 new features and status -- please help me make a list

[Deep Debroy <ddebroy@xxxxxxxxx>]

On Sat, Sep 8, 2012 at 5:26 AM, Gianluca Guida <glguida@xxxxxxxxxxxx> wrote:
>
> On Fri, Sep 07, 2012 at 04:51:15PM +0100, Ian Campbell wrote:
> > On Fri, 2012-09-07 at 16:49 +0100, Jan Beulich wrote:
> > > >>> On 07.09.12 at 17:39, Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> > > >>> wrote:
> > > >> > vMSI: ? Emulated (or real?) MSIs for guests?
> > > >> >         State? New in 4.2?
> > > >>
> > > >> Not sure what you're referring to here. There certainly was a
> > > >> xen/arch/x86/hvm/vmsi.c in 4.1 already.
> > > >
> > > > OK, thanks. 4.0 too by the looks of it.
> > > >
> > > > What exactly is this? Is it about injection of MSIs from real
> > > > (passthrough) hardware devices to guests (only HVM ones?) or is
> > > > about
> > > > MSIs generated by emulated devices (or both)?
> > >
> > > I don't think emulated devices genera MSIs, so to me this is
> > > just for passthrough. But I may be wrong.
> >
> > It sounds plausible to me ;-)
>
> There is in 4.2 an HVM op to generate MSIs from emulated devices, added
> at changeset 23413.
> The passthrough part was already present before.

Quick clarification about emulated devices using MSI: the emulation of
vmware's paravirtualized scsi controller, pvscsi, in qemu (submitted
as patches but not in the official qemu tree yet) uses MSI. Changeset
25588 was necessary in xen to get MSIs to flow from the pvscsi
emulation in qemu to xen vms running the upstream vmware pvscsi driver
in the linux kernel.

Thanks,
Deep

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