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Mon, 30 Mar 2020 20:58:16 +0000 (UTC) Received: from w520.home (ovpn-112-162.phx2.redhat.com [10.3.112.162]) by smtp.corp.redhat.com (Postfix) with ESMTP id 05F9F5C1BB; Mon, 30 Mar 2020 20:58:14 +0000 (UTC) Date: Mon, 30 Mar 2020 14:58:14 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH v17 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Message-ID: <20200330145814.32d9b652@w520.home> In-Reply-To: <1585587044-2408-7-git-send-email-kwankhede@nvidia.com> References: <1585587044-2408-1-git-send-email-kwankhede@nvidia.com> <1585587044-2408-7-git-send-email-kwankhede@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 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 Mon, 30 Mar 2020 22:20:43 +0530 Kirti Wankhede wrote: > Flag VFIO_IOMMU_INFO_DIRTY_PGS in VFIO_IOMMU_GET_INFO indicates that driver > support dirty pages tracking. > > Signed-off-by: Kirti Wankhede > Reviewed-by: Neo Jia > --- > drivers/vfio/vfio_iommu_type1.c | 3 ++- > include/uapi/linux/vfio.h | 5 +++-- > 2 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 266550bd7307..9fe12b425976 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -2390,7 +2390,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data, > info.cap_offset = 0; /* output, no-recopy necessary */ > } > > - info.flags = VFIO_IOMMU_INFO_PGSIZES; > + info.flags = VFIO_IOMMU_INFO_PGSIZES | > + VFIO_IOMMU_INFO_DIRTY_PGS; > > info.iova_pgsizes = vfio_pgsize_bitmap(iommu); > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index e3cbf8b78623..0fe7c9a6f211 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -985,8 +985,9 @@ struct vfio_device_feature { > struct vfio_iommu_type1_info { > __u32 argsz; > __u32 flags; > -#define VFIO_IOMMU_INFO_PGSIZES (1 << 0) /* supported page sizes info */ > -#define VFIO_IOMMU_INFO_CAPS (1 << 1) /* Info supports caps */ > +#define VFIO_IOMMU_INFO_PGSIZES (1 << 0) /* supported page sizes info */ > +#define VFIO_IOMMU_INFO_CAPS (1 << 1) /* Info supports caps */ > +#define VFIO_IOMMU_INFO_DIRTY_PGS (1 << 2) /* supports dirty page tracking */ > __u64 iova_pgsizes; /* Bitmap of supported page sizes */ > __u32 cap_offset; /* Offset within info struct of first cap */ > }; As I just mentioned in my reply to Yan, I'm wondering if VFIO_CHECK_EXTENSION would be a better way to expose this. The difference is relatively trivial, but currently the only flag set by VFIO_IOMMU_GET_INFO is to indicate the presence of a field in the returned structure. I think this is largely true of other INFO ioctls within vfio as well and we're already using the VFIO_CHECK_EXTENSION ioctl to check supported IOMMU models, and IOMMU cache coherency. We'd simply need to define a VFIO_DIRTY_PGS_IOMMU value (9) and return 1 for that case. Then when we enable support for dirt pages that can span multiple mappings, we can add a v2 extensions, or "MULTI" variant of this extension, since it should be backwards compatible. The v2/multi version will again require that the user provide a zero'd bitmap, but I don't think that should be a problem as part of the definition of that version (we won't know if the user is using v1 or v2, but a v1 user should only retrieve bitmaps that exactly match existing mappings, where all bits will be written). Thanks, Alex