Messages in this thread |  | | | From | Rusty Russell <> | | Subject | Re: [PATCH] virtio-pci: Use PCI MMIO instead of PIO when available | | Date | Thu, 13 Oct 2011 10:22:36 +1030 |
| |
On Wed, 12 Oct 2011 14:39:06 +1100, Alexey Kardashevskiy <aik@ozlabs.ru> wrote: > Currently virtio-pci is specced so that configuration of the device is > done through a PCI IO space (via BAR 0 of the virtual PCI device). > However, use of PCI IO space (aka PIO) is long deprecated, and can be > awkward to use on some systems (for example IBM pSeries machines > typically have many PCI domains, and not all firmware/hypervisor > versions necessarily support PCI PIO access on all domains). > > Therefore, it would be preferable for the virtio virtual PCI device to > advertise a PCI memory space (aka MMIO) BAR and have configuration > done through this interface instead. This can be done backwards > compatibly by advertising the MMIO BAR in addition to the existing PIO > BAR so that the guest driver can choose whichever interface. > > In anticipation of adding such an MMIO BAR to virtio host-side > implementations (e.g. qemu), this patch updates the Linux virtio-pci > driver to attempt to use BAR 2 (which will be MMIO) in preference to > the existing PIO BAR 0.
Applied. Had to convert spaces to tabs though...
Thanks, Rusty.
|  |