From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 0C0F3B70C7 for ; Tue, 2 Aug 2011 11:29:13 +1000 (EST) Subject: Re: kvm PCI assignment & VFIO ramblings From: Benjamin Herrenschmidt To: Alex Williamson In-Reply-To: <1312216847.2653.258.camel@bling.home> References: <1311983933.8793.42.camel@pasglop> <1312064479.8793.739.camel@pasglop> <1312216847.2653.258.camel@bling.home> Content-Type: text/plain; charset="UTF-8" Date: Tue, 02 Aug 2011 11:29:00 +1000 Message-ID: <1312248540.8793.828.camel@pasglop> Mime-Version: 1.0 Cc: Alexey Kardashevskiy , kvm@vger.kernel.org, Paul Mackerras , "linux-pci@vger.kernel.org" , David Gibson , Anthony Liguori , linuxppc-dev List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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.