Re: [Xen-devel] [Query] How does Xen X86 does pci enumeration

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Jul 22, 2014 at 03:21:31PM +0530, Xenbegn developer wrote:
> On Wed, Jul 16, 2014 at 7:19 PM, Konrad Rzeszutek Wilk <
> konrad.wilk@xxxxxxxxxx> wrote:
> 
> > On Wed, Jul 16, 2014 at 05:25:07PM +0530, Xenbegn developer wrote:
> > > On 7/15/14, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
> > > > On Tue, Jul 15, 2014 at 11:54:34AM +0530, Xenbegn developer wrote:
> > > >> Hi,
> > > >>
> > > >> Small beginner query. Where in Xen X86 code pci ep enumeration is
> > done?
> > > >> I believe it this should be the flow of events
> > > >> a)  from ACPI enumerate all the PCI controllers
> > > >> b) On each Controller start enumerating the pci devices.
> > > >
> > > > No. You can also query the PCI via the configuration registers.
> > > >
> > > > Look in the 'pci.c' files.
> > > >>
> > > >> I started from _start_xen in arch/x86/setup.c but couldnt find the top
> > > >> level function.
> > > >> Can anyone please provide pointer.
> > > >>
> > > One supplement question, does Xen do PCI devices enumeration or Dom0
> > does it ?
> >
> > Both.
> >
> 
> What is the use case for dom0 and xen both to do pci devices enumeration.
> What purpose it solves for xen ?

To figure out which PCI interrupts should be assigned to the guest and also
do the MSI and MSI-X writes to the BAR space of PCI devices - instead of
the guest doing it.

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