From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: [PATCH 4/4] kvm/vfio: Support for DMA coherent IOMMUs Date: Mon, 17 Feb 2014 13:24:12 -0700 Message-ID: <20140217202412.22775.77911.stgit@bling.home> References: <20140217201324.22775.31904.stgit@bling.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Paolo Bonzini , linux-kernel@vger.kernel.org To: alex.williamson@redhat.com, kvm@vger.kernel.org Return-path: In-Reply-To: <20140217201324.22775.31904.stgit@bling.home> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org VFIO now has support for using the IOMMU_CACHE flag and a mechanism for an external user to test the current operating mode of the IOMMU. Add support for this to the kvm-vfio pseudo device so that we only register noncoherent DMA when necessary. Signed-off-by: Alex Williamson Cc: Gleb Natapov Cc: Paolo Bonzini --- virt/kvm/vfio.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-) diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c index b4f9507..ba1a93f 100644 --- a/virt/kvm/vfio.c +++ b/virt/kvm/vfio.c @@ -59,6 +59,22 @@ static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group) symbol_put(vfio_group_put_external_user); } +static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group) +{ + long (*fn)(struct vfio_group *, unsigned long); + long ret; + + fn = symbol_get(vfio_external_check_extension); + if (!fn) + return false; + + ret = fn(vfio_group, VFIO_DMA_CC_IOMMU); + + symbol_put(vfio_external_check_extension); + + return ret > 0; +} + /* * Groups can use the same or different IOMMU domains. If the same then * adding a new group may change the coherency of groups we've previously @@ -75,13 +91,10 @@ static void kvm_vfio_update_coherency(struct kvm_device *dev) mutex_lock(&kv->lock); list_for_each_entry(kvg, &kv->group_list, node) { - /* - * TODO: We need an interface to check the coherency of - * the IOMMU domain this group is using. For now, assume - * it's always noncoherent. - */ - noncoherent = true; - break; + if (!kvm_vfio_group_is_coherent(kvg->vfio_group)) { + noncoherent = true; + break; + } } if (noncoherent != kv->noncoherent) {