Re: [Xen-devel] Notes from PCI Passthrough design discussion at Xen Summit

[Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>]

HI Julien,

On 7/20/2017 4:11 PM, Julien Grall wrote:
> On 20/07/17 10:32, Manish Jaggi wrote:
> > Hi Roger,
> >
> > On 7/20/2017 1:54 PM, Roger Pau Monné wrote:
> > > On Thu, Jul 20, 2017 at 09:24:36AM +0530, Manish Jaggi wrote:
> > > > Hi Punit,
> > > >
> > > > On 7/19/2017 8:11 PM, Punit Agrawal wrote:
> > > > > I took some notes for the PCI Passthrough design discussion at Xen
> > > > > Summit. Due to the wide range of topics covered, the notes got 
> > > > > sparser
> > > > > towards the end of the session. I've tried to attribute names against
> > > > > comments but have very likely got things mixed up. Apologies in
> > > > > advance.
> > > > Was curious if any discussions happened on the RC Emu (config space
> > > > emulation) as per slide 18
> > > > https://schd.ws/hosted_files/xendeveloperanddesignsummit2017/76/slides.pdf 
> > > Part of this is already posted on the list (ATM for x86 only) but the
> > > PCI specification (and therefore the config space emulation) is not
> > > tied to any arch:
> > >
> > > https://lists.xenproject.org/archives/html/xen-devel/2017-06/msg03698.html 
> > From the summary, I have a  questions on
> > "
> >  - Roger: Registering config space with Xen before device discovery
> >   will allow the hypervisor to set access traps for certain
> >  functionality as appropriate"
> >
> > Traps will do emulation or something else ?
> >  Is the config space emulation only for DomU or it for Dom0 as well ?
> > Slide 18 shows only for DomU ?
> My slides are not meant to be read without the talk. In this 
> particular case, this is only explaining how passthrough will work for 
> DomU.
Thanks for clarification.
Ah ok, The single slide created confusion, It would be nice if you have 
added one more describing dom0 config access. I will wait for the video 
to get posted.
> Roger series is at the moment focusing on emulating a fully ECAM 
> compliant hostbridge for the hardware domain. This is because Xen and 
> the hardware domain should not access the configuration space at the 
> same time. 
Yes as discussed on this topic on list few weeks back.
> We may also perform some tasks (i.e MSI mapping, memory mapping) or 
> sanitizing when the configuration space is updated by the hardware 
> domain.
> Cheers,

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