From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47513) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WsXRc-000524-HW for qemu-devel@nongnu.org; Thu, 05 Jun 2014 09:11:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WsXRO-0000Xg-LM for qemu-devel@nongnu.org; Thu, 05 Jun 2014 09:11:00 -0400 Received: from mail-pb0-f47.google.com ([209.85.160.47]:64888) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WsXRO-0000X4-EK for qemu-devel@nongnu.org; Thu, 05 Jun 2014 09:10:46 -0400 Received: by mail-pb0-f47.google.com with SMTP id rp16so1100431pbb.34 for ; Thu, 05 Jun 2014 06:10:45 -0700 (PDT) Message-ID: <53906C50.50308@ozlabs.ru> Date: Thu, 05 Jun 2014 23:10:40 +1000 From: Alexey Kardashevskiy MIME-Version: 1.0 References: <1401947401-21329-1-git-send-email-aik@ozlabs.ru> <1401947401-21329-2-git-send-email-aik@ozlabs.ru> <5390119D.8040201@ozlabs.ru> <53906B56.3080007@suse.de> In-Reply-To: <53906B56.3080007@suse.de> Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v7 1/4] spapr_iommu: Make in-kernel TCE table optional List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf , qemu-devel@nongnu.org Cc: Alex Williamson , qemu-ppc@nongnu.org, Gavin Shan On 06/05/2014 11:06 PM, Alexander Graf wrote: > > On 05.06.14 08:43, Alexey Kardashevskiy wrote: >> On 06/05/2014 03:49 PM, Alexey Kardashevskiy wrote: >>> POWER KVM supports an KVM_CAP_SPAPR_TCE capability which allows allocating >>> TCE tables in the host kernel memory and handle H_PUT_TCE requests >>> targeted to specific LIOBN (logical bus number) right in the host without >>> switching to QEMU. At the moment this is used for emulated devices only >>> and the handler only puts TCE to the table. If the in-kernel H_PUT_TCE >>> handler finds a LIOBN and corresponding table, it will put a TCE to >>> the table and complete hypercall execution. The user space will not be >>> notified. >>> >>> Upcoming VFIO support is going to use the same sPAPRTCETable device class >>> so KVM_CAP_SPAPR_TCE is going to be used as well. That means that TCE >>> tables for VFIO are going to be allocated in the host as well. >>> However VFIO operates with real IOMMU tables and simple copying of >>> a TCE to the real hardware TCE table will not work as guest physical >>> to host physical address translation is requited. >>> >>> So until the host kernel gets VFIO support for H_PUT_TCE, we better not >>> to register VFIO's TCE in the host. >>> >>> This adds a bool @kvm_accel flag to the sPAPRTCETable device telling >>> that sPAPRTCETable should not try allocating TCE table in the host kernel. >>> Instead, the table will be created in QEMU. >>> >>> This adds an kvm_accel parameter to spapr_tce_new_table() to let users >>> choose whether to use acceleration or not. At the moment it is enabled >>> for VIO and emulated PCI. Upcoming VFIO support will set it to false. >>> >>> Signed-off-by: Alexey Kardashevskiy >>> --- >>> >>> This is a workaround but it lets me have one IOMMU device for VIO, emulated >>> PCI and VFIO which is a good thing. >>> >>> The other way around would be a new KVM_CAP_SPAPR_TCE_VFIO capability but >>> this needs kernel update. >> >> Never mind, I'll make it a capability. I'll post capability reservation >> patch separately. > > Just rename the flag from "kvm_accel" to "vfio_accel", set it to true for > vfio and false for emulated devices. Then the spapr_iommu file can check on > the capability (and default to false for now, since it doesn't exist yet). Is that ok if the flag does not have to do anything with VFIO per se? :) > That way you don't have to reserve a CAP today. Why exactly cannot we do that today? How do we proceed with the rest of this patchset? Thanks! -- Alexey