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Tue, 31 Mar 2020 19:06:27 +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 889775C1BB; Tue, 31 Mar 2020 19:06:25 +0000 (UTC) Date: Tue, 31 Mar 2020 13:06:25 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH v17 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200331130625.77851747@w520.home> In-Reply-To: <66af06b5-4e87-9f7a-be85-08a68d6ab982@nvidia.com> References: <1585587044-2408-1-git-send-email-kwankhede@nvidia.com> <1585587044-2408-6-git-send-email-kwankhede@nvidia.com> <20200330153421.6246c2c6@w520.home> <66af06b5-4e87-9f7a-be85-08a68d6ab982@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] [fuzzy] X-Received-From: 207.211.31.120 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 Wed, 1 Apr 2020 00:16:13 +0530 Kirti Wankhede wrote: > On 3/31/2020 3:04 AM, Alex Williamson wrote: > > On Mon, 30 Mar 2020 22:20:42 +0530 > > Kirti Wankhede wrote: > > > >> DMA mapped pages, including those pinned by mdev vendor drivers, might > >> get unpinned and unmapped while migration is active and device is still > >> running. For example, in pre-copy phase while guest driver could access > >> those pages, host device or vendor driver can dirty these mapped pages. > >> Such pages should be marked dirty so as to maintain memory consistency > >> for a user making use of dirty page tracking. > >> > >> To get bitmap during unmap, user should allocate memory for bitmap, set > >> size of allocated memory, set page size to be considered for bitmap and > >> set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP. > >> > >> Signed-off-by: Kirti Wankhede > >> Reviewed-by: Neo Jia > >> --- > >> drivers/vfio/vfio_iommu_type1.c | 55 ++++++++++++++++++++++++++++++++++++++--- > >> include/uapi/linux/vfio.h | 10 ++++++++ > >> 2 files changed, 61 insertions(+), 4 deletions(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >> index 5efebc2b60e1..266550bd7307 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -983,7 +983,8 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size) > >> } > >> > >> static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> - struct vfio_iommu_type1_dma_unmap *unmap) > >> + struct vfio_iommu_type1_dma_unmap *unmap, > >> + struct vfio_bitmap *bitmap) > >> { > >> uint64_t mask; > >> struct vfio_dma *dma, *dma_last = NULL; > >> @@ -1034,6 +1035,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> * will be returned if these conditions are not met. The v2 interface > >> * will only return success and a size of zero if there were no > >> * mappings within the range. > >> + * > >> + * When VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP flag is set, unmap request > >> + * must be for single mapping. Multiple mappings with this flag set is > >> + * not supported. > >> */ > >> if (iommu->v2) { > >> dma = vfio_find_dma(iommu, unmap->iova, 1); > >> @@ -1041,6 +1046,14 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> ret = -EINVAL; > >> goto unlock; > >> } > >> + > >> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >> + dma && > >> + (dma->iova != unmap->iova || dma->size != unmap->size)) { > > > > > > I think your intention was to return error if the user asked for the > > dirty bitmap and the requested unmap range doesn't exactly match the > > vfio_dma. Not finding a vfio_dma should therefore also be an error. > > For example, if we had a single mapping at {0x1000-0x1fff} and the user > > unmapped with dirty bitmap {0x0-0x2fff}, that should return an error, > > but it's not caught by the above because there is no vfio_dma @0x0. > > Therefore I think you want: > > > > ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > > (!dma || dma->iova != unmap->iova || dma->size != unmap->size)) > > > > Right? Thanks, > > > > > Yes, updating check. > > Is !dma here also error case when VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP > flag is not set? No it's not. > DMA_UNMAP ioctl returns how much was unmapped, from user space > perspective this would be from start of range (unmap->iova), right? It's the actual amount of memory that was unmapped within the provided range, without getting the dirty bitmap the range doesn't need to start or end at a vfio_dma, it just cannot bisect a vfio_dma. Thanks, Alex