[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Query] Flow of PCI device dedicated to a domU
On 7/16/14, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: > On 16/07/14 07:12, Xenbegn developer wrote: >> Hi, >> I am trying to understand the flow of how a PCI device driver in domU >> works after a PCI device is is assigned to a domU. >> >> a) If a PCI device is assigned to a domU, this device has to be on a >> PCI bus. So as per my view xen would have to somehow provide a PCI >> Controller on which this device is attached. >> => Is my assumption correct ? If yes how it is done, No then also How >> enumeration of this device happens in domU kernel > > No. > > PV guests have no PCI root ports/bridges; they use devices as single > entities knowing that Xen/dom0 takes care of the other bits. HVM guests > have their PCI devices attached to the virtual southbridge which is all > emulated by Qemu. > How would a then a PV guest know about existence of a PCI device if it does not enumerate. Can you please elaborate on this. >> >> b) Is the Configuration space of the PCI device directly accessible to >> the domU (assuming the kernel accesses it using memory map) ? If not >> then it is trapped by xen > > All configuration space is trap+emulate in Xen, although almost all > operations permitted. > >> >> c) Who assigns the MSI (addr + value) in the PCI device. If Xen then >> how Xen does a translation from Physical MSI to guest MSI (where in code) > > Xen controls all interrupts on the system, which is why it needs to trap > all config accesses to notice when a domain is attempting to change the > interrupt information. In that case, Xen fixes up its delivery of > interrupts to the guest, but leaves the underlying interrupt information > intact. > > ~Andrew > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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