On Mon, Nov 06, 2017 at 04:44:03PM +1100, Alexey Kardashevskiy wrote: > On 16/10/17 19:01, David Gibson wrote: > > On Mon, Oct 16, 2017 at 06:36:29PM +1100, Alexey Kardashevskiy wrote: > >> On 16/10/17 17:00, David Gibson wrote: > >>> On Mon, Oct 16, 2017 at 04:54:08PM +1100, Alexey Kardashevskiy wrote: > >>>> On 12/10/17 02:35, Benjamin Herrenschmidt wrote: > >>>>> On Wed, 2017-10-11 at 13:56 +1100, Alexey Kardashevskiy wrote: > >>>>>> Oopsie. This is because I overlooked it. Others do not use it. So I do need > >>>>>> a file. But in the current scheme where all BARs share one fd - it won't > >>>>>> work - I simply cannot allow WC on non-prefetchable BARs :-/ > >>>>> > >>>>> This is an oversight in the design of VFIO-PCI, it should have a way to > >>>>> specify write combine, either implicitely via such an arch hook, or > >>>>> explicitely via an ioctl prior to mapping the BARs for example. > >>>>> > >>>>> Alex, what do you reckon is the best approach here ? > >>>> > >>>> /me wonders if it is yet another issue for the dead issues bucket, just > >>>> like the msix mapping one :) > >>> > >>> Maybe. Alexey, maybe you can make up a list of things that we (me, > >>> you, BenH) need to discuss with Alex W at KVM Forum? > >> > >> "you" - you meant me? I am not coming over there :( > > > > Oh.. I thought you were. > > > >> The list is: > >> > >> 1. Allow msix mapping to the userspace (to address non-64k-aligned msix bar) We have a new plan on this - I'll discuss it over IRC. > >> 2. Allow write combining in vfio for the userspace (kvm guest is kinda > >> special and may simply ignore mapping flags in some configs but PPC radix > >> guests still rely on this) AIUI this isn't for radix, but for DPDK things that we need this. Ben talked about it a bit, but I don't know what the outcome was. > >> 3. what callback and where needs to be added to inform HV/PR KVM about VFIO > >> group, like IOMMUMR::add_vfio_group() proposal or something. This was discussed, and I'm still thinking about it. It's kind of curly. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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