From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759312Ab3E1Xau (ORCPT ); Tue, 28 May 2013 19:30:50 -0400 Received: from mail-pb0-f44.google.com ([209.85.160.44]:39466 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759267Ab3E1Xas (ORCPT ); Tue, 28 May 2013 19:30:48 -0400 Message-ID: <51A53E20.3020205@ozlabs.ru> Date: Wed, 29 May 2013 09:30:40 +1000 From: Alexey Kardashevskiy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130402 Thunderbird/17.0.5 MIME-Version: 1.0 To: Scott Wood CC: David Gibson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, Alexander Graf , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 3/4] KVM: PPC: Add support for IOMMU in-kernel handling References: <1369763138.18630.3@snotra> In-Reply-To: <1369763138.18630.3@snotra> Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/29/2013 03:45 AM, Scott Wood wrote: > On 05/26/2013 09:44:24 PM, Alexey Kardashevskiy wrote: >> On 05/25/2013 12:45 PM, David Gibson wrote: >> > On Wed, May 22, 2013 at 04:06:57PM -0500, Scott Wood wrote: >> >> On 05/20/2013 10:06:46 PM, Alexey Kardashevskiy wrote: >> >>> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c >> >>> index 8465c2a..da6bf61 100644 >> >>> --- a/arch/powerpc/kvm/powerpc.c >> >>> @@ -396,6 +396,7 @@ int kvm_dev_ioctl_check_extension(long ext) >> >>> +++ b/arch/powerpc/kvm/powerpc.c >> >>> break; >> >>> #endif >> >>> case KVM_CAP_SPAPR_MULTITCE: >> >>> + case KVM_CAP_SPAPR_TCE_IOMMU: >> >>> r = 1; >> >>> break; >> >>> default: >> >> >> >> Don't advertise SPAPR capabilities if it's not book3s -- and >> >> probably there's some additional limitation that would be >> >> appropriate. >> > >> > So, in the case of MULTITCE, that's not quite right. PR KVM can >> > emulate a PAPR system on a BookE machine, and there's no reason not to >> > allow TCE acceleration as well. We can't make it dependent on PAPR >> > mode being selected, because that's enabled per-vcpu, whereas these >> > capabilities are queried on the VM before the vcpus are created. >> > >> > CAP_SPAPR_TCE_IOMMU should be dependent on the presence of suitable >> > host side hardware (i.e. a PAPR style IOMMU), though. >> >> >> The capability says that the ioctl is supported. If there is no IOMMU group >> registered, than it will fail with a reasonable error and nobody gets hurt. >> What is the problem? > > You could say that about a lot of the capabilities that just advertise the > existence of new ioctls. :-) > > Sometimes it's nice to know in advance whether it's supported, before > actually requesting that something happen. Yes, would be nice. There is just no quick way to know if this real system supports IOMMU groups. I could add another helper to generic IOMMU code which would return the number of registered IOMMU groups but it is a bit too much :) >> >>> @@ -939,6 +940,9 @@ struct kvm_s390_ucas_mapping { >> >>> #define KVM_GET_DEVICE_ATTR _IOW(KVMIO, 0xe2, struct >> >>> kvm_device_attr) >> >>> #define KVM_HAS_DEVICE_ATTR _IOW(KVMIO, 0xe3, struct >> >>> kvm_device_attr) >> >>> >> >>> +/* ioctl for SPAPR TCE IOMMU */ >> >>> +#define KVM_CREATE_SPAPR_TCE_IOMMU _IOW(KVMIO, 0xe4, struct >> >>> kvm_create_spapr_tce_iommu) >> >> >> >> Shouldn't this go under the vm ioctl section? >> >> >> The KVM_CREATE_SPAPR_TCE_IOMMU ioctl (the version for emulated devices) is >> in this section so I decided to keep them together. Wrong? > > You decided to keep KVM_CREATE_SPAPR_TCE_IOMMU together with > KVM_CREATE_SPAPR_TCE_IOMMU? Yes. -- Alexey