From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: kvm PCI assignment & VFIO ramblings Date: Tue, 02 Aug 2011 11:29:00 +1000 Message-ID: <1312248540.8793.828.camel@pasglop> References: <1311983933.8793.42.camel@pasglop> <1312064479.8793.739.camel@pasglop> <1312216847.2653.258.camel@bling.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Alexey Kardashevskiy , kvm@vger.kernel.org, Paul Mackerras , "linux-pci@vger.kernel.org" , David Gibson , Anthony Liguori , linuxppc-dev To: Alex Williamson Return-path: In-Reply-To: <1312216847.2653.258.camel@bling.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Sender: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org List-Id: kvm.vger.kernel.org On Mon, 2011-08-01 at 10:40 -0600, Alex Williamson wrote: > On Sun, 2011-07-31 at 08:21 +1000, Benjamin Herrenschmidt wrote: > > On Sat, 2011-07-30 at 09:58 +1000, Benjamin Herrenschmidt wrote: > > > Hi folks ! > > > > > > So I promised Anthony I would try to summarize some of the comments & > > > issues we have vs. VFIO after we've tried to use it for PCI pass-through > > > on POWER. It's pretty long, there are various items with more or less > > > impact, some of it is easily fixable, some are API issues, and we'll > > > probably want to discuss them separately, but for now here's a brain > > > dump. > > > > > > David, Alexei, please make sure I haven't missed anything :-) > > > > And I think I have :-) > > > > * Config space > > > > VFIO currently handles that as a byte stream. It's quite gross to be > > honest and it's not right. You shouldn't lose access size information > > between guest and host when performing real accesses. > > > > Some config space registers can have side effects and not respecting > > access sizes can be nasty. > > It's a bug, let's fix it. Right. I was just trying to be exhaustive :-) If you don't beat us to it, we'll eventually submit patches to fix it, we haven't fixed it yet either, just something I noticed (because this byte-transport also makes handling of endianess clumsly). Cheers, Ben.