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Wed, 18 Dec 2019 00:12:22 +0000 (UTC) Received: from x1.home (ovpn-116-53.phx2.redhat.com [10.3.116.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id 717AC6106B; Wed, 18 Dec 2019 00:12:20 +0000 (UTC) Date: Tue, 17 Dec 2019 17:12:19 -0700 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH v11 Kernel 6/6] vfio: Selective dirty page tracking if IOMMU backed device pins pages Message-ID: <20191217171219.7cc3fc1d@x1.home> In-Reply-To: <1576602651-15430-7-git-send-email-kwankhede@nvidia.com> References: <1576602651-15430-1-git-send-email-kwankhede@nvidia.com> <1576602651-15430-7-git-send-email-kwankhede@nvidia.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com, yi.l.liu@intel.com, cjia@nvidia.com, kvm@vger.kernel.org, eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org, cohuck@redhat.com, shuangtai.tst@alibaba-inc.com, dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com, aik@ozlabs.ru, eauger@redhat.com, felipe@nutanix.com, jonathan.davies@nutanix.com, yan.y.zhao@intel.com, changpeng.liu@intel.com, Ken.Xue@amd.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 17 Dec 2019 22:40:51 +0530 Kirti Wankhede wrote: > Track dirty pages reporting capability for each vfio_device by setting the > capability flag on calling vfio_pin_pages() for that device. > > In vfio_iommu_type1 module, while creating dirty pages bitmap, check if > IOMMU backed device is present in the container. If IOMMU backed device is > present in container then check dirty pages reporting capability for each > vfio device in the container. If all vfio devices are capable of reporing > dirty pages tracking by pinning pages through external API, then report > create bitmap of pinned pages only. If IOMMU backed device is present in > the container and any one device is not able to report dirty pages, then > marked all pages as dirty. > > Signed-off-by: Kirti Wankhede > Reviewed-by: Neo Jia > --- > drivers/vfio/vfio.c | 33 +++++++++++++++++++++++++++++++ > drivers/vfio/vfio_iommu_type1.c | 44 +++++++++++++++++++++++++++++++++++++++-- > include/linux/vfio.h | 3 ++- > 3 files changed, 77 insertions(+), 3 deletions(-) > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > index c8482624ca34..9d2fbe09768a 100644 > --- a/drivers/vfio/vfio.c > +++ b/drivers/vfio/vfio.c > @@ -96,6 +96,8 @@ struct vfio_device { > struct vfio_group *group; > struct list_head group_next; > void *device_data; > + /* dirty pages reporting capable */ > + bool dirty_pages_cap; > }; > > #ifdef CONFIG_VFIO_NOIOMMU > @@ -1866,6 +1868,29 @@ int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, int num_irqs, > } > EXPORT_SYMBOL(vfio_set_irqs_validate_and_prepare); > > +int vfio_device_is_dirty_reporting_capable(struct device *dev, bool *cap) > +{ > + struct vfio_device *device; > + struct vfio_group *group; > + > + if (!dev || !cap) > + return -EINVAL; > + > + group = vfio_group_get_from_dev(dev); > + if (!group) > + return -ENODEV; > + > + device = vfio_group_get_device(group, dev); > + if (!device) > + return -ENODEV; > + > + *cap = device->dirty_pages_cap; > + vfio_device_put(device); > + vfio_group_put(group); > + return 0; > +} > +EXPORT_SYMBOL(vfio_device_is_dirty_reporting_capable); I'd suggest this just return true/false and any error condition simply be part of the false case. > + > /* > * Pin a set of guest PFNs and return their associated host PFNs for local > * domain only. > @@ -1907,6 +1932,14 @@ int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage, > else > ret = -ENOTTY; > > + if (ret > 0) { > + struct vfio_device *device = vfio_group_get_device(group, dev); > + > + if (device) { > + device->dirty_pages_cap = true; > + vfio_device_put(device); > + } > + } I think we'd want to trivially rework vfio_pin_pages() to use vfio_device_get_from_dev() instead of vfio_group_get_from_dev(), then we have access to the group via device->group. Then vfio_device_put() would be common in the return path. > vfio_group_try_dissolve_container(group); > > err_pin_pages: > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 68d8ed3b2665..ef56f31f4e73 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -891,6 +891,39 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu) > return bitmap; > } > > +static int vfio_is_dirty_pages_reporting_capable(struct device *dev, void *data) > +{ > + bool new; > + int ret; > + > + ret = vfio_device_is_dirty_reporting_capable(dev, &new); > + if (ret) > + return ret; > + > + *(bool *)data = *(bool *)data && new; > + > + return 0; > +} > + > +static bool vfio_dirty_pages_reporting_capable(struct vfio_iommu *iommu) > +{ > + struct vfio_domain *d; > + struct vfio_group *g; > + bool capable = true; > + int ret; > + > + list_for_each_entry(d, &iommu->domain_list, next) { > + list_for_each_entry(g, &d->group_list, next) { > + ret = iommu_group_for_each_dev(g->iommu_group, &capable, > + vfio_is_dirty_pages_reporting_capable); > + if (ret) > + return false; This will fail when there are devices within the IOMMU group that are not represented as vfio_devices. My original suggestion was: On Thu, 14 Nov 2019 14:06:25 -0700 Alex Williamson wrote: > I think it does so by pinning pages. Is it acceptable that if the > vendor driver pins any pages, then from that point forward we consider > the IOMMU group dirty page scope to be limited to pinned pages? There > are complications around non-singleton IOMMU groups, but I think we're > already leaning towards that being a non-worthwhile problem to solve. > So if we require that only singleton IOMMU groups can pin pages and we We could tag vfio_groups as singleton at vfio_add_group_dev() time with an iommu_group_for_each_dev() walk so that we can cache the value on the struct vfio_group. vfio_group_nb_add_dev() could update this if the IOMMU group composition changes. vfio_pin_pages() could return -EINVAL if (!group->is_singleton). > pass the IOMMU group as a parameter to > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a > flag on its local vfio_group struct to indicate dirty page scope is > limited to pinned pages. ie. vfio_iommu_type1_unpin_pages() calls find_iommu_group() on each domain in domain_list and the external_domain using the struct iommu_group pointer provided by vfio-core. We set a new attribute on the vfio_group to indicate that vfio_group has (at some point) pinned pages. > We might want to keep a flag on the > vfio_iommu struct to indicate if all of the vfio_groups for each > vfio_domain in the vfio_iommu.domain_list dirty page scope limited to > pinned pages as an optimization to avoid walking lists too often. Then > we could test if vfio_iommu.domain_list is not empty and this new flag > does not limit the dirty page scope, then everything within each > vfio_dma is considered dirty. So at the point where we change vfio_group.has_pinned_pages from false to true, or a group is added or removed, we walk all the groups in the vfio_iommu and if they all have has_pinned_pages set, we can set a vfio_iommu.pinned_page_dirty_scope flag to true. If that flag is already true on page pinning, we can skip the lookup. I still like this approach better, it doesn't require a callback from type1 to vfio-core and it doesn't require a heavy weight walking for group devices and vfio data structures every time we fill a bitmap. Did you run into issues trying to implement this approach? Thanks, Alex > + } > + } > + > + return capable; > +} > + > /* > * start_iova is the reference from where bitmaping started. This is called > * from DMA_UNMAP where start_iova can be different than iova > @@ -903,10 +936,17 @@ static void vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova, > struct vfio_dma *dma; > dma_addr_t i = iova; > unsigned long pgshift = __ffs(pgsize); > + bool dirty_report_cap = true; > + > + if (IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)) > + dirty_report_cap = vfio_dirty_pages_reporting_capable(iommu); > > while ((dma = vfio_find_dma(iommu, i, pgsize))) { > - /* mark all pages dirty if all pages are pinned and mapped. */ > - if (dma->iommu_mapped) { > + /* > + * mark all pages dirty if any IOMMU capable device is not able > + * to report dirty pages and all pages are pinned and mapped. > + */ > + if (!dirty_report_cap && dma->iommu_mapped) { > dma_addr_t iova_limit; > > iova_limit = (dma->iova + dma->size) < (iova + size) ? > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > index e42a711a2800..ed3832ea10a1 100644 > --- a/include/linux/vfio.h > +++ b/include/linux/vfio.h > @@ -148,7 +148,8 @@ extern int vfio_info_add_capability(struct vfio_info_cap *caps, > extern int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, > int num_irqs, int max_irq_type, > size_t *data_size); > - > +extern int vfio_device_is_dirty_reporting_capable(struct device *dev, > + bool *cap); > struct pci_dev; > #if IS_ENABLED(CONFIG_VFIO_SPAPR_EEH) > extern void vfio_spapr_pci_eeh_open(struct pci_dev *pdev);