On Fri, Feb 23, 2018 at 12:55 AM, Haozhong Zhang <haozhong.zhang@xxxxxxxxx> wrote: > On 02/22/18 23:17 -0800, Dan Williams wrote: >> Changes since v1 [1]: >> >> * Fix the detection of device-dax file instances in vma_is_fsdax(). >> (Haozhong, Gerd) >> >> * Fix compile breakage in the FS_DAX=n and DEV_DAX=y case. (0day robot) >> >> [1]: https://lists.01.org/pipermail/linux-nvdimm/2018-February/014046.html >> >> --- >> >> The vfio interface, like RDMA, wants to setup long term (indefinite) >> pins of the pages backing an address range so that a guest or userspace >> driver can perform DMA to the with physical address. Given that this >> pinning may lead to filesystem operations deadlocking in the >> filesystem-dax case, the pinning request needs to be rejected. >> >> The longer term fix for vfio, RDMA, and any other long term pin user, is >> to provide a 'pin with lease' mechanism. Similar to the leases that are >> hold for pNFS RDMA layouts, this userspace lease gives the kernel a way >> to notify userspace that the block layout of the file is changing and >> the kernel is revoking access to pinned pages. >> >> --- >> >> Dan Williams (5): >> dax: fix vma_is_fsdax() helper >> dax: fix dax_mapping() definition in the FS_DAX=n + DEV_DAX=y case >> dax: fix S_DAX definition >> dax: short circuit vma_is_fsdax() in the CONFIG_FS_DAX=n case >> vfio: disable filesystem-dax page pinning >> >> >> drivers/vfio/vfio_iommu_type1.c | 18 +++++++++++++++--- >> include/linux/dax.h | 9 ++++++--- >> include/linux/fs.h | 6 ++++-- >> 3 files changed, 25 insertions(+), 8 deletions(-) > > Tested on QEMU with fs-dax and device-dax as vNVDIMM backends > respectively with vfio passthrough. The fs-dax case fails QEMU as > expected, and the device-dax case works normally now. > > Tested-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx> > Thank you!