From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59667) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ysrwj-0003ET-4T for qemu-devel@nongnu.org; Thu, 14 May 2015 08:09:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ysrwf-0003Mc-R9 for qemu-devel@nongnu.org; Thu, 14 May 2015 08:09:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43353) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ysrwf-0003M2-MG for qemu-devel@nongnu.org; Thu, 14 May 2015 08:08:57 -0400 Message-ID: <55549051.1090007@redhat.com> Date: Thu, 14 May 2015 14:08:49 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1431516714-25816-1-git-send-email-drjones@redhat.com> <20150514103018.GM32765@cbox> <5554826E.1040706@redhat.com> <20150514112910.GR32765@cbox> <55548777.9000702@redhat.com> <20150514113634.GS32765@cbox> <5554893E.4030105@redhat.com> <20150514120039.GU32765@cbox> In-Reply-To: <20150514120039.GU32765@cbox> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christoffer Dall Cc: peter.maydell@linaro.org, Andrew Jones , ard.biesheuvel@linaro.org, marc.zyngier@arm.com, catalin.marinas@arm.com, "Michael S. Tsirkin" , qemu-devel@nongnu.org, agraf@suse.de, j.fanguede@virtualopensystems.com, Laszlo Ersek , kvmarm@lists.cs.columbia.edu, m.smarduch@samsung.com On 14/05/2015 14:00, Christoffer Dall wrote: > So, getting back to my original question. Is the point then that UEFI > must assume (from ACPI/DT) the cache-coherency properties of the PCI > controller which exists in hardware on the system you're running on, > even for the virtual PCI bus because that will be the semantics for > assigned devices? > > And in that case, we have no way to distinguish between passthrough > devices and virtual devices plugged into the virtual PCI bus? Well, we could use the subsystem id. But it's a hack, and may cause incompatibilities with some drivers. Michael, any ideas? > What about the idea of having two virtual PCI buses on your system where > one is always cache-coherent and uses for virtual devices, and the other > is whatever the hardware is and used for passthrough devices? I think that was rejected before. Paolo