From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:48542 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727976AbgF2Smj (ORCPT ); Mon, 29 Jun 2020 14:42:39 -0400 Subject: Re: [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature References: <1592390637-17441-1-git-send-email-pmorel@linux.ibm.com> <1592390637-17441-2-git-send-email-pmorel@linux.ibm.com> <20200618002956.5f179de4.pasic@linux.ibm.com> <20200619112051.74babdb1.cohuck@redhat.com> <7fe6e9ab-fd5a-3f92-1f3a-f9e6805d3730@linux.ibm.com> <20200629154439.14cc5ae7.cohuck@redhat.com> From: Pierre Morel Message-ID: <4777633f-728b-1a67-c870-0fafa313e468@linux.ibm.com> Date: Mon, 29 Jun 2020 18:10:02 +0200 MIME-Version: 1.0 In-Reply-To: <20200629154439.14cc5ae7.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Cornelia Huck Cc: Halil Pasic , linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, mst@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, thomas.lendacky@amd.com, david@gibson.dropbear.id.au, linuxram@us.ibm.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com On 2020-06-29 15:44, Cornelia Huck wrote: > On Mon, 29 Jun 2020 15:14:04 +0200 > Pierre Morel wrote: > >> On 2020-06-19 11:20, Cornelia Huck wrote: >>> On Thu, 18 Jun 2020 00:29:56 +0200 >>> Halil Pasic wrote: >>> >>>> On Wed, 17 Jun 2020 12:43:57 +0200 >>>> Pierre Morel wrote: > >>>>> @@ -179,6 +194,13 @@ int virtio_finalize_features(struct virtio_device *dev) >>>>> if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) >>>>> return 0; >>>>> >>>>> + if (arch_needs_virtio_iommu_platform(dev) && >>>>> + !virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) { >>>>> + dev_warn(&dev->dev, >>>>> + "virtio: device must provide VIRTIO_F_IOMMU_PLATFORM\n"); > > [Side note: wasn't there a patch renaming this bit on the list? I think > this name is only kept for userspace compat.] Sorry, I do not understand what you expect from me. On which mailing list you think there is a patch on? > >>>> >>>> I'm not sure, divulging the current Linux name of this feature bit is a >>>> good idea, but if everybody else is fine with this, I don't care that >>> >>> Not sure if that feature name will ever change, as it is exported in >>> headers. At most, we might want to add the new ACCESS_PLATFORM define >>> and keep the old one, but that would still mean some churn. >>> >>>> much. An alternative would be: >>>> "virtio: device falsely claims to have full access to the memory, >>>> aborting the device" >>> >>> "virtio: device does not work with limited memory access" ? >>> >>> But no issue with keeping the current message. >>> >> >> If it is OK, I would like to specify that the arch is responsible to >> accept or not the device. >> The reason why the device is not accepted without IOMMU_PLATFORM is arch >> specific. > > Hm, I'd think the reason is always the same (the device cannot access > the memory directly), just the way to figure out whether that is the > case or not is arch-specific, as with so many other things. No real > need to go into detail here, I think. > As you like, so I rename the subject to: "virtio: device does not work with limited memory access" Regards, Pierre -- Pierre Morel IBM Lab Boeblingen