Re: [Xen-devel] [DRAFT RFC] PVHv2 interaction with physical devices

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.11.16 at 17:49, <roger.pau@xxxxxxxxxx> wrote:
> On Fri, Nov 11, 2016 at 03:04:49AM -0700, Jan Beulich wrote:
>> >>> On 10.11.16 at 18:21, <konrad.wilk@xxxxxxxxxx> wrote:
>> > On Thu, Nov 10, 2016 at 04:20:34PM +0100, Roger Pau Monné wrote:
>> >> > 0a:11.4 Ethernet controller: Intel Corporation 82576 Virtual Function
>> >> > (rev 01)
>> >> >         Subsystem: Super Micro Computer Inc Device 10c9
>> >> >         Flags: bus master, fast devsel, latency 0
>> >> >         [virtual] Memory at fbdb8000 (64-bit, non-prefetchable) 
>> >> > [size=16K]
>> >> >         [virtual] Memory at fbd98000 (64-bit, non-prefetchable) 
>> >> > [size=16K]
>> >> >         Capabilities: [70] MSI-X: Enable+ Count=3 Masked-
>> >> >         Capabilities: [a0] Express Endpoint, MSI 00
>> >> >         Capabilities: [100] Advanced Error Reporting
>> >> >         Capabilities: [150] Alternative Routing-ID Interpretation (ARI)
>> >> >         Kernel driver in use: igbvf
>> >> 
>> >> So it seems that the memory for individual VFs is taken from the BARs 
>> >> listed 
>> >> inside of PCI_EXT_CAP_ID_SRIOV.
>> > 
>> > Yup! I think that is right as the BIOS also enable SR-IOV to figure out how
>> > many bus addresses to reserve for the PCIe device - and then it turn it 
>> > off.
>> > (I know this as I had a motherboard with half-broken implemention that 
>> > booted
>> > in OS with VFs already there).
>> 
>> But remember that in the common case you won't be able to access
>> the SR-IOV capability structure before launching Dom0 (as being
>> located in extended config space).
> 
> Since we need PHYSDEVOP_pci_mmcfg_reserved anyway, the newly added bus will 
> be 
> scanned in order to find devices, and those SR-IOV BARs will be added then 
> into 
> the Dom0 memory map.

You mean you want to rescan bus ranges when that hypercall gets
issued, even when that range had been scanned already? Doable,
but you'll need to carefully handle possible changes you observe on
the 2nd scan compared to the 1st.

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel