On Tue, 29 Sep 2020 09:27:02 +0100 Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: > On Fri, May 29, 2020 at 02:00:46AM +0530, Kirti Wankhede wrote: > > * IOCTL VFIO_IOMMU_DIRTY_PAGES to get dirty pages bitmap with > > respect to IOMMU container rather than per device. All pages pinned by > > vendor driver through vfio_pin_pages external API has to be marked as > > dirty during migration. When IOMMU capable device is present in the > > container and all pages are pinned and mapped, then all pages are marked > > dirty. > > From what I can tell only the iommu participates in dirty page tracking. > This places the responsibility for dirty page tracking on IOMMUs. My > understanding is that support for dirty page tracking is currently not > available in IOMMUs. > > Can a PCI device implement its own DMA dirty log and let an mdev driver > implement the dirty page tracking using this mechanism? That way we > don't need to treat all pinned pages as dirty all the time. Look at the last patch in this series, there we define a mechanism whereby the act of a vendor driver pinning pages both marks those pages dirty and indicates a mode in the vfio type1 container where the scope of dirty pages is limited to those pages pinned by the driver. The vfio_dma_rw() interface does the same. We could clearly implement a more lightweight interface for this as well, one without pinning or memory access, but there are no proposed users for such an interface currently. Thanks, Alex
