From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED Date: Thu, 14 May 2015 14:08:49 +0200 Message-ID: <55549051.1090007@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 0FA2651498 for ; Thu, 14 May 2015 07:59:51 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 75wpNzT9W3R5 for ; Thu, 14 May 2015 07:59:50 -0400 (EDT) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 074BD50A2A for ; Thu, 14 May 2015 07:59:49 -0400 (EDT) In-Reply-To: <20150514120039.GU32765@cbox> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Christoffer Dall Cc: ard.biesheuvel@linaro.org, marc.zyngier@arm.com, catalin.marinas@arm.com, "Michael S. Tsirkin" , qemu-devel@nongnu.org, Laszlo Ersek , kvmarm@lists.cs.columbia.edu List-Id: kvmarm@lists.cs.columbia.edu 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