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

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
Was curious if any discussions happened on the RC Emu (config space
emulation) as per slide 18

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:


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.


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