On Wed, Sep 06, 2023 at 10:55:26AM +0200, Cédric Le Goater wrote: > > + WARN_ON(node); > > + log_addr_space_size = ilog2(total_ranges_len); > > + if (log_addr_space_size < > > + (MLX5_CAP_ADV_VIRTUALIZATION(mdev, pg_track_log_min_addr_space)) || > > + log_addr_space_size > > > + (MLX5_CAP_ADV_VIRTUALIZATION(mdev, pg_track_log_max_addr_space))) { > > + err = -EOPNOTSUPP; > > + goto out; > > + } > > > We are seeing an issue with dirty page tracking when doing migration > of an OVMF VM guest. The vfio-pci variant driver for the MLX5 VF > device complains when dirty page tracking is initialized from QEMU : > > qemu-kvm: 0000:b1:00.2: Failed to start DMA logging, err -95 (Operation not supported) > > The 64-bit computed range is : > > vfio_device_dirty_tracking_start nr_ranges 2 32:[0x0 - 0x807fffff], 64:[0x100000000 - 0x3838000fffff] > > which seems to be too large for the HW. AFAICT, the MLX5 HW has a 42 > bits address space limitation for dirty tracking (min is 12). Is it a > FW tunable or a strict limitation ? It would be good to explain where this is coming from, all devices need to make some decision on what address space ranges to track and I would say 2^42 is already pretty generous limit.. Can we go the other direction and reduce the ranges qemu is interested in? Jason